PDF Editing Issues

Fix Acrobat Operation Not Permitted When Comparing PDF Documents

Steve K Oct 22, 2026 868 views

Question details

The user is trying to compare two PDF documents in Adobe Acrobat Pro DC but receives a 'This operation is not permitted' error message, preventing the comparison.

How to Fix 'Operation Not Permitted' When Comparing PDFs in Acrobat

Product: Adobe Acrobat Pro DC
Device & OS: not provided
Scenario: Using the Compare Files tool to find differences between two PDF versions.
Observed behavior: Acrobat blocks the action and displays an error stating 'This operation is not permitted'.

Before you start

Ensure you have the passwords for both PDF files if they are encrypted, and verify that the files open correctly on their own without showing signs of corruption.

Solution 1Recommended

Remove Document Security Restrictions

If either of the PDF documents is secured against copying or editing, Acrobat cannot compare them. You must remove these restrictions first.

PDFs are often protected with permission passwords to prevent unauthorized edits or data extraction. The Compare Files tool requires full access to the text and formatting in both documents. If these permissions are restricted, the operation will be blocked by the software.

Check Document Properties

Open the first PDF in Acrobat, go to 'File' > 'Properties' in the top menu, and click on the 'Security' tab.

Verify Restrictions

Look at the 'Document Restrictions Summary' to see if 'Changing the Document' or 'Content Copying' is set to 'Not Allowed'.

Remove Security

If restricted, change the Security Method drop-down to 'No Security'. You will need to enter the permissions password if prompted, then click 'OK' and save the document.

Repeat and Compare

Repeat this process for the second PDF file, then attempt to use the 'Compare Files' tool again.

Password Requirement: You must be the owner of the document or know the permission password to legally remove security restrictions.

Solution 2

Update Adobe Acrobat DC to the Latest Build

Older versions of Acrobat DC had known bugs with the compare feature that have been resolved in subsequent updates.

Advanced PDF Management

Seamlessly View and Compare PDFs with WPS Office

If Acrobat restrictions continue to block your workflow, WPS Office offers an incredibly fast and lightweight PDF solution. You can easily view documents side-by-side, extract text, and manage your PDF files without frustrating permission bugs.

1. Download and Install: Download WPS Office for free and launch the WPS PDF application on your computer.
2. Open Your PDFs: Open both PDF files you want to compare. They will open in separate document tabs at the top.
3. Enable Side-by-Side View: Go to the 'View' tab on the ribbon and select the 'Side-by-Side' option, or simply drag one tab to the edge of the screen to split the window.
4. Compare Documents: Scroll through both documents simultaneously to visually compare their contents without triggering restriction errors.

View multiple PDF documents side-by-side for easy visual comparison.Fully compatible with standard PDF formats and Adobe Acrobat files.Lightweight software that opens large documents instantly.Comprehensive suite for handling PDFs, Word documents, Excel sheets, and more.

Frequently Asked Questions

Why does Adobe Acrobat say a PDF operation is not permitted?

This error usually occurs because the author of the PDF applied security settings to prevent editing, copying, or extracting content. Acrobat requires these exact permissions to analyze and compare the files programmatically.

Can I compare a signed PDF document?

Digitally signed or certified PDFs are locked to prevent tampering. Comparing them often triggers restriction errors because the software cannot process the locked content. You may need to use an original, unsigned version for the comparison.

Is there a way to bypass PDF security to compare documents?

Acrobat requires you to legally remove the security by entering the correct permissions password in the Document Properties menu. Without the password, the secure restrictions cannot be bypassed natively.

Does the Acrobat Compare tool work with scanned PDFs?

Yes, but only if Optical Character Recognition (OCR) has been applied first. Without OCR, Acrobat sees the pages as flat images and cannot compare the actual text differences.

PDF Troubleshooting