PDF Editing Issues

How to Check if a PDF Letter Was Changed in Adobe Acrobat

Emma Brown Oct 19, 2026 868 views

Question details

The user wants to know how to identify modifications made to a PDF document after it was shared with someone else.

How to Check Whether a PDF Letter Was Changed in Adobe Acrobat

Product: Adobe Acrobat
Device & OS: not provided
Scenario: Comparing a received PDF copy against an original reference file to spot unauthorized or expected edits.
Observed behavior: The user needs a method to highlight differences in text, formatting, and other document elements between two versions of the same PDF file.

Before you start

Ensure you have the original, unchanged version of the PDF letter saved on your local drive, as you will need it to serve as the baseline for your document comparison.

Solution 1Recommended

Use the Compare Files Feature in Adobe Acrobat Desktop

Adobe Acrobat includes a built-in comparison tool that scans two PDF files and generates a report highlighting all structural and text differences.

This feature allows you to instantly spot what has been added, deleted, or modified. Note that the Compare Files feature is exclusive to the premium desktop version of Adobe Acrobat and is not available in Acrobat Reader or the mobile app.

Open Adobe Acrobat

Launch the Adobe Acrobat desktop application on your computer.

Access the Compare Tool

Navigate to the 'Tools' menu at the top of the window and select the 'Compare Files' tool.

Select the Original File

Click 'Select File' on the left side of the screen and choose your original reference PDF letter.

Select the Changed File

Click 'Select File' on the right side and choose the received PDF copy that you want to check for modifications.

Run the Comparison

Click the 'Compare' button. Acrobat will analyze both documents and present a summary page detailing all text, image, and formatting changes.

Use the Compare Files Feature in Adobe Acrobat Desktop

Version Limitations: If you are using the free Acrobat Reader, the Compare Files feature will be unavailable. You must upgrade to a premium version or use an alternative PDF solution to compare files.

Manage and Compare PDFs Effectively with WPS Office

WPS Office provides a comprehensive, lightweight PDF editor that allows you to easily view, manage, and edit your PDF documents alongside Word, Excel, and PowerPoint files in one single application.

1. Install WPS Office: Download and install WPS Office on your computer, then launch the application.
2. Open Your Original PDF: Click 'Open' and select your original PDF letter to load it into the WPS PDF editor.
3. Open the Modified PDF: Open the received PDF copy in a new tab within the same WPS Office window.
4. View Side-by-Side: Go to the 'View' tab and select the split-screen or multi-window mode to visually compare the documents and use annotation tools to mark any discrepancies.

View documents side-by-side to manually inspect changes easily.Fully compatible with standard Adobe PDF formats and Microsoft Office files.Lightweight application that loads large PDF documents incredibly fast.Built-in annotation tools to track changes, highlight text, and add comments.

microsoft office alternative - wps office

Frequently Asked Questions

Can I compare PDFs using the free Adobe Acrobat Reader?

No, the Compare Files feature is only available in the paid desktop versions of Adobe Acrobat (such as Acrobat Standard or Acrobat Pro). Acrobat Reader is limited to viewing, commenting, and printing.

Can I check for PDF changes on my mobile phone?

The Compare Files tool is not currently supported in the Acrobat mobile app. You will need to use a desktop application to automatically highlight differences between PDF documents.

What types of changes does the PDF comparison tool detect?

The Acrobat comparison tool typically detects changes in text, fonts, images, formatting, and page order, highlighting them in an easy-to-read visual summary report.

How can I prevent others from changing my PDF letter in the first place?

You can restrict editing by going to the PDF's security properties (File > Properties > Security) and setting a permissions password, which prevents unauthorized modifications to the document.

PDF Troubleshooting