Combining, Splitting, and Compressing PDFs: A Practical Guide

10 Sep 2026

PDF files are convenient because they preserve a document’s layout across different computers, phones and operating systems. However, they can quickly become awkward when several files need to be combined, one large document must be divided into smaller sections, or an attachment is too large to email.

Fortunately, combining, splitting and compressing PDFs does not usually require expensive specialist software. Many everyday tasks can be completed using built-in operating-system tools, office applications, trusted desktop utilities or carefully selected online services.

This guide explains how to merge PDF files, extract individual pages, divide large documents and reduce PDF file sizes without unnecessarily damaging quality.

What Does Combining a PDF Mean?

Combining PDFs means joining two or more separate files into one document.

For example, you may want to combine:

A report and its appendices
An invoice and supporting evidence
Several scanned pages
A contract and signature pages
Multiple application documents
A proposal, quotation and terms
Monthly statements
Project handover documents

The finished PDF contains all the selected pages in the order you choose.

Combining files can make documents easier to:

Send
Store
Review
Print
Upload
Archive
Share with clients

However, the pages should always be reviewed after merging to confirm that nothing is missing, duplicated or out of order.

What Does Splitting a PDF Mean?

Splitting a PDF means dividing one file into two or more smaller documents.

You may need to split a PDF when:

It contains records for several customers
Only one chapter needs to be shared
An application includes several separate forms
A scanned batch contains multiple invoices
Confidential pages must be separated
One section needs to be sent to another department
The file is too large for an upload system
Individual documents need separate filenames

Splitting can involve:

Extracting selected pages
Saving every page as a separate PDF
Dividing the file into fixed page ranges
Separating chapters
Removing unwanted pages
Creating smaller sections based on file size

What Does Compressing a PDF Mean?

Compressing a PDF reduces its file size.

A large PDF may contain:

High-resolution photographs
Full-colour scans
Embedded fonts
Duplicate images
Hidden data
Attached files
Unnecessary metadata
Very detailed graphics

Compression may reduce the size by:

Lowering image resolution
Recompressing images
Removing unused content
Simplifying embedded data
Converting colour pages to greyscale
Removing attachments or comments
Optimising the PDF structure

The challenge is reducing the file size without making the document difficult to read.

Why PDF Files Become So Large

A text-only PDF can be extremely small. A scanned or image-heavy file can become hundreds of megabytes.

Common causes include:

High-Resolution Scans

A scanner set to 600 or 1,200 dots per inch can create very large files.

For ordinary text documents, such high resolution is rarely necessary.

Full-Colour Scanning

A black-and-white letter scanned in full colour stores far more information than needed.

Phone Camera Images

Photographs taken with a modern smartphone may be several megabytes each.

Placing many full-resolution images inside a document can produce an enormous PDF.

Uncompressed Images

Some applications embed images with minimal compression.

Large Drawings and Graphics

Architectural plans, technical diagrams and vector illustrations may contain significant detail.

Embedded Fonts

PDFs may include complete font files to preserve the design.

Repeated Editing

Some software retains old document information, layers or revisions.

Attachments

A PDF can contain embedded spreadsheets, images or other files that may not be obvious from the page view.

Before You Edit Any PDF

Always keep the original.

Create a copy with a clear filename, such as:

Project Report - Original.pdf

and:

Project Report - Working Copy.pdf

This protects you if:

Pages are removed accidentally
Compression damages image quality
The page order becomes incorrect
A digital signature is invalidated
The application overwrites the original
Important metadata or form fields disappear

For business documents, keep the source file and approved final version separately.

How to Combine PDF Files

The exact process depends on the device and software, but the basic workflow is consistent.

Select the PDFs.
Arrange them in the correct order.
Merge the files.
Save the result under a new name.
Open the combined PDF.
Check every page.

Plan the Page Order First

Before merging, decide how the final document should be structured.

For example:

1. Cover page

2. Executive summary

3. Main report

4. Appendix A

5. Appendix B

6. Terms and conditions

Rename files temporarily if necessary:

01 Cover.pdf

02 Report.pdf

03 Appendix A.pdf

04 Appendix B.pdf

Numbered filenames make the intended order clearer.

Check Page Sizes

A combined PDF may contain a mixture of:

A4 portrait
A4 landscape
Letter size
Legal size
Scanned receipts
Oversized diagrams

Different page sizes are not automatically wrong, but the result may look inconsistent.

Check whether pages should remain at their original size or be resized before merging.

Combining PDFs on macOS

Apple Preview can combine PDF documents.

A typical process is:

Open the first PDF in Preview.
Show the thumbnail sidebar.
Open the second PDF.
Drag its page thumbnails into the first document.
Arrange the pages.
Save or export the combined file.

You can also drag selected pages rather than the complete document.

Always use Save As or export a new copy when the original must remain unchanged.

Combining PDFs on Windows

Windows does not always provide one universal built-in merge button, but several approaches are available.

You can use:

A trusted desktop PDF utility
A business-approved PDF application
Microsoft Print to PDF for limited workflows
A browser-based service for non-sensitive files
An office application when the original files can be recreated

Printing documents into one PDF may work for simple page sets, but it can remove interactive elements such as:

Links
Bookmarks
Form fields
Accessibility tags
Digital signatures

A dedicated merge function is preferable when these features matter.

Combining Scanned Pages

When several scans belong to one document:

Rotate each page correctly.
Remove blank pages.
Check that no page was scanned twice.
Confirm the sequence.
Crop excessive borders.
Run optical character recognition where required.
Use consistent scan quality.

If the pages contain text only, greyscale or black-and-white scanning may significantly reduce file size.

How to Split a PDF

Splitting can be performed by page number, range or section.

Extract Selected Pages

Suppose a 100-page manual contains the section you need on pages 36 to 48.

You can extract that range and save it as:

Manual - Installation Section.pdf

A common method is:

Open the PDF.
Choose Print.
Enter the selected page range.
Select a PDF printer or Save as PDF.
Save the new file.

This method creates a visual copy of the selected pages.

It may remove:

Bookmarks
Forms
Links
Layers
Digital signatures
Accessibility structure

Use a proper page-extraction function when these features need to be preserved.

Save Individual Pages

Some tools can split every page into its own PDF.

For example:

Invoice Batch - Page 001.pdf

Invoice Batch - Page 002.pdf

Invoice Batch - Page 003.pdf

This is useful for scanned invoice batches, but you may then need to rename the files according to their contents.

Split by Page Range

A large document might be divided like this:

Part 1 - Pages 1 to 50

Part 2 - Pages 51 to 100

Part 3 - Pages 101 to 150

This is useful for systems with page-count or file-size limits.

Split by Chapter

When the PDF contains bookmarks or a structured contents list, some applications can create separate files for each chapter.

This may produce more meaningful results than fixed page ranges.

Delete Unwanted Pages

When you need most of the PDF, it may be simpler to delete a few pages from a copy.

Examples include:

Blank scanner pages
Obsolete appendices
Duplicate cover pages
Internal notes
Instruction sheets
Unwanted advertising

After deleting pages:

Save a new version.
Reopen it.
Check the page numbers.
Search for removed information.
Confirm that references and the contents page still make sense.

Separating Confidential Pages

Splitting a PDF can help separate content intended for different audiences.

For example, a report may contain:

General findings
Customer contact details
Financial information
Internal technical notes
Staff information

Do not assume that simply extracting the public pages removes all confidential information.

Also inspect:

Comments
Attachments
Metadata
Hidden layers
Form data
Bookmarks
Document properties

When confidential text appears on a page that must otherwise be shared, proper redaction may be required.

Compression vs. Reducing Image Quality

PDF compression is not always lossless.

Some optimisation methods remove unnecessary data without visibly changing the file. Others reduce image quality.

Lossless Optimisation

Lossless changes may include:

Removing unused objects
Compressing document structure
Removing duplicate data
Cleaning metadata
Optimising fonts
Removing hidden elements

The document should look the same afterward.

Lossy Compression

Lossy compression may:

Lower image resolution
Increase JPEG compression
Reduce colour depth
Convert images to greyscale
Remove fine visual detail

The result is smaller, but some quality is lost.

For ordinary on-screen documents, moderate lossy compression may be acceptable. For print, technical drawings or archive copies, preserve a high-quality original.

How Much Should You Compress a PDF?

The right file size depends on how the document will be used.

Email Attachment

A smaller file is easier to send, but text and signatures must remain readable.

Website Download

The file should load quickly without making images unnecessarily blurry.

Customer Portal

Check the portal’s maximum upload size.

Printing

Preserve enough resolution for the intended paper size.

Archive

Keep the highest-quality practical version.

Technical Drawings

Avoid aggressive compression that removes fine lines or labels.

Legal and Financial Records

Maintain legibility and ensure that signatures, dates and amounts remain clear.

Practical PDF Compression Methods

Remove Unnecessary Pages

The simplest way to reduce file size is to remove pages that are not needed.

Reduce Image Resolution

Large images are frequently the main cause of oversized PDFs.

For normal office documents viewed on screen, extremely high image resolution is unnecessary.

Convert Colour Scans to Greyscale

When colour adds no meaningful information, greyscale can reduce the file size significantly.

Do not convert pages where colour communicates:

Warnings
Chart categories
Branding requirements
Evidence
Annotations
Signatures
Medical information
Wiring or technical diagrams

Recreate the PDF From the Source

When the original Word, PowerPoint or design file exists, export it again using an appropriate PDF setting.

You may see options such as:

Standard
Minimum size
Print quality
Screen quality
Optimised for online publishing

Re-exporting from the source often produces a better result than repeatedly compressing an existing PDF.

Resize Images Before Creating the PDF

A document does not need a 20-megapixel photograph when the image appears only a few centimetres wide.

Resize large images before inserting them into the source document.

Remove Comments and Attachments

Comments, embedded documents and attachments may increase the file size.

Remove them only when they are not required.

Flatten Unneeded Interactive Content

Flattening may reduce complexity in some documents, but it can also remove:

Form fields
Links
Accessibility
Layers
Signatures

Keep an editable copy.

Compressing Scanned PDFs

Scanned documents often offer the greatest opportunity for file-size reduction.

Use Appropriate Scan Resolution

For ordinary text:

Around 200 to 300 dpi is usually a practical range.
Higher resolutions may help with small print or OCR.
Extremely high settings are rarely needed for office documents.

Use Black and White for Simple Text

Black-and-white scanning can create small files for clean printed pages.

It may perform poorly with:

Faded originals
Pencil writing
Photographs
Coloured stamps
Light signatures
Shaded backgrounds

Use Greyscale for Mixed Text

Greyscale often provides a good balance for documents containing:

Signatures
Light handwriting
Shading
Older paper
Stamps
Photocopied material

Avoid Repeated Scanning and Compression

Every lossy processing step can reduce quality.

Scan the original once using sensible settings and keep that master copy.

Using Online PDF Tools Safely

Online tools can be convenient for merging, splitting and compressing.

However, uploading a PDF means sending it to another organisation’s systems.

Avoid unknown online services for files containing:

Customer data
Financial information
Contracts
Payroll records
Identification documents
Medical information
Security details
Passwords
Confidential reports
Employee information

For sensitive files, use:

A trusted local application
Approved company software
An organisational Microsoft 365 workflow
A managed document system
A secure internal service

Questions to Ask Before Uploading

Check:

Is the connection encrypted?
Where is the file processed?
How long is it retained?
Is it deleted automatically?
Can staff access uploaded documents?
Is the content used for training?
Is the service approved by your organisation?
Is an account required?
Is there a clear privacy policy?

A free service may be convenient, but convenience does not guarantee confidentiality.

Protecting Digitally Signed PDFs

A digital signature confirms that a document has not been altered since signing.

Combining, splitting, compressing or rearranging the PDF may invalidate that signature.

Before changing a signed document:

Keep the signed original.
Check whether alteration is permitted.
Confirm the required legal or business process.
Request the unsigned source when necessary.
Do not suggest that the old signature covers the new version.

A visible image of a handwritten signature is different from a cryptographic digital signature.

Compression and PDF Forms

Interactive PDF forms may contain:

Text fields
Checkboxes
Dropdowns
Calculations
Validation
Submit buttons
Signature fields

Some compression or print-to-PDF methods flatten the document and remove these features.

Before compressing a form, decide whether the recipient needs to:

Complete it
Edit existing answers
Sign it
Submit it electronically
Use calculations

Keep both versions when necessary:

Application Form - Editable.pdf

Application Form - Completed Record.pdf

Combining PDFs With Different Security Settings

Some PDFs may be:

Password protected
Restricted from editing
Restricted from copying
Digitally signed
Encrypted

You may be unable to combine them without appropriate permissions or passwords.

Do not attempt to bypass security restrictions.

Request an authorised copy or obtain the necessary access from the document owner.

Adding Bookmarks After Combining PDFs

A large merged PDF can become difficult to navigate.

Bookmarks can create links to:

Cover page
Executive summary
Main report
Appendices
Terms
Supporting documents

For customer or internal reports, bookmarks improve usability significantly.

Some free tools do not preserve or create them, so check the final result.

Fixing Page Orientation

Combined scans frequently contain sideways or upside-down pages.

Rotate pages individually before or after combining them.

Confirm that the rotation is saved permanently rather than applied only as a temporary viewing setting.

Handling Mixed Portrait and Landscape Pages

A report may contain portrait text pages and landscape tables.

This is acceptable when intentional.

Check:

Whether landscape pages open correctly
Whether page numbers remain readable
Whether printing settings handle rotation
Whether the document fits on standard paper
Whether users can read it without excessive zooming

Do not rotate a legitimate landscape table into portrait merely to make every page look identical.

Maintaining Quality When Combining PDFs

Combining alone should not necessarily reduce quality.

However, some tools rebuild or recompress every page.

Check the merged result for:

Blurry text
Soft images
Colour shifts
Missing links
Changed fonts
Altered page sizes
Flattened forms
Broken signatures
Reduced accessibility

Use a tool that preserves the original PDF pages where quality matters.

How to Check a Compressed PDF

Never assume compression worked correctly because the file is smaller.

Open the finished file and inspect:

Small text
Signatures
Tables
Charts
Images
Fine lines
Barcodes
QR codes
Dates
Currency values
Page numbers
Scanned handwriting

Zoom in and compare it with the original.

Also print a sample when the document will be printed.

Check Barcodes and QR Codes

Aggressive compression can make barcodes and QR codes unreadable.

After compression:

Scan every important code.
Check that it links to the correct location.
Confirm printed versions still work.
Avoid resizing codes too small.

This is especially important for:

Tickets
Shipping labels
Payment documents
Asset tags
Event registrations

File Naming After Combining or Splitting

Use clear names.

For a combined file:

2026 Project Handover Pack.pdf

For split sections:

2026 Project Handover - Main Report.pdf

2026 Project Handover - Appendix A.pdf

2026 Project Handover - Support Documents.pdf

For a compressed version:

Project Report - Email Copy.pdf

Keep the high-quality original:

Project Report - Print Master.pdf

Avoid filenames such as:

new-final-small-final2.pdf

Keep a High-Quality Master

Compression should normally create a delivery copy rather than replacing the best version.

A practical structure is:

Project Report - Source.docx

Project Report - Print Master.pdf

Project Report - Email Copy.pdf

The print master preserves quality.

The email copy is optimised for convenient sharing.

Common PDF Combining Mistakes

Pages in the Wrong Order

Always preview the complete document.

Duplicate Pages

Scanned batches frequently include repeated pages.

Missing Appendices

Compare the final page count with the expected total.

Mixed Versions

Do not accidentally combine a draft section with an approved report.

Broken Page Numbers

A report’s internal numbering may no longer match the merged document.

Invalidated Signatures

Combining signed files can affect signature validity.

Lost Bookmarks

Some tools remove existing navigation.

Exposed Confidential Data

A merged pack may include pages intended only for internal use.

Common PDF Splitting Mistakes

Sharing the Wrong Page Range

Check actual page content rather than relying only on displayed numbers.

A document’s printed page 1 may not be PDF page 1 because of covers or front matter.

Losing Context

An extracted section may refer to definitions or diagrams in another section.

Leaving Confidential Metadata

Extracted pages may still retain document properties or attachments.

Breaking Signed Documents

Extracting pages can invalidate verification.

Removing Required Terms

A quotation without its terms may be incomplete.

Common PDF Compression Mistakes

Overcompressing Images

Text and diagrams may become blurry.

Compressing the Only Copy

Keep the original.

Flattening Forms Accidentally

The recipient may no longer be able to complete them.

Damaging Accessibility

Tags, reading order and bookmarks may disappear.

Making Signatures Unreadable

Fine handwriting may be lost.

Trusting File Size Alone

A tiny PDF is not useful when the content is unreadable.

Uploading Sensitive Files to Unknown Services

Use approved tools for confidential data.

A Practical Workflow for Combining PDFs

Create a working folder.
Copy the source files into it.
Rename files in the intended order.
Check that each file opens.
Remove unwanted pages.
Rotate pages correctly.
Merge the files.
Save under a new name.
Compare the page count.
Review every page.
Check links, forms and bookmarks.
Confirm no confidential content was included.
Save the approved version securely.

A Practical Workflow for Splitting PDFs

Keep the original file.
Identify the required page ranges.
Check the content of each boundary page.
Extract or print the selected pages.
Name each new file clearly.
Open every output file.
Confirm that no pages are missing.
Check confidential information.
Verify that links and forms still work where required.
Store the original and split copies appropriately.

A Practical Workflow for Compressing PDFs

Keep the original high-quality file.
Check what is making the PDF large.
Remove unnecessary pages or attachments.
Try lossless optimisation first.
Reduce image resolution moderately.
Save as a new file.
Compare file sizes.
Inspect text, diagrams and signatures.
Test barcodes and QR codes.
Print a sample where necessary.
Use the compressed version only for its intended purpose.

Which Method Should You Use?

You Need to Send Several Documents Together

Combine them into one clearly ordered PDF.

You Need Only One Section

Extract the required pages.

You Need Every Invoice Separately

Split the file into individual documents and rename them.

The PDF Is Too Large to Email

Create a moderately compressed delivery copy.

The PDF Contains Confidential Data

Use an approved local tool and inspect metadata and attachments.

The PDF Is Digitally Signed

Keep the signed original and confirm whether changes are allowed.

The PDF Is a Form

Avoid methods that flatten interactive fields unless a fixed completed copy is intended.

The PDF Contains Technical Drawings

Use conservative compression and check fine detail.

Free Tools vs. Paid PDF Software

Free or built-in tools are often sufficient for:

Simple merging
Page extraction
Page rotation
Basic compression
Printing selected pages
Creating ordinary PDF copies

Paid software may be worthwhile when you frequently need:

Batch processing
Automated splitting
Professional redaction
OCR
Accessibility tools
Form creation
Document comparison
Digital signature management
Advanced compression controls
Business deployment
Technical support

The right choice depends on the volume, sensitivity and complexity of the work.

PDF Management Checklist

Before editing:

Keep the original.
Confirm the required output.
Check for signatures.
Check for forms.
Review the sensitivity of the content.
Choose an approved tool.
Confirm the intended page order or ranges.

After editing:

Open every output file.
Check the page count.
Review the page order.
Inspect text and images.
Test links and forms.
Check bookmarks.
Verify signatures.
Review metadata and attachments.
Test barcodes.
Confirm the file size.
Use a clear filename.
Store it securely.

Final Thoughts

Combining, splitting and compressing PDFs are straightforward tasks when you use a careful process.

Combining PDFs creates a single organised document from several files. Splitting allows you to extract only the pages or sections that need to be shared. Compression makes oversized PDFs easier to email, upload and store.

The most important rule is to preserve the original.

Do not aggressively compress the only copy, modify a digitally signed document without checking the consequences or upload confidential information to an unknown website. Always review the finished file and confirm that pages, signatures, forms, images and important details remain intact.

A few minutes of checking can prevent missing pages, unreadable scans and accidental disclosure of sensitive information.

Need Help Managing PDF Documents?

Large, badly organised or sensitive PDF files can create problems with email, storage, printing and secure sharing.

Hamilton Group can help businesses organise documents, convert and optimise PDF files, improve Microsoft 365 workflows and create reliable document-management processes.

Visit hgmssp.com, call 0330 043 0069, or book a meeting with one of our experts.

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