Why PDF File Size Increases After Adding Digital Signatures & How to Fix
Question details
The user wants to understand why their PDF document size inflates significantly after applying PKCS#7 digital signatures and how to resolve it.
- Product
- Device & OS
- not provided
- Scenario
- Applying, removing, and reapplying digital signatures to a single PDF document during a signing workflow.
- Observed behavior
- The PDF file size grows from a few megabytes to hundreds of megabytes because each signature embeds previous document revisions.
Verify the current size of your PDF document and make sure you have a backup copy of the original file before removing signatures or saving over it.
Use 'Save As' to Remove Accumulated Revision Data
Using the 'Save As' command generates a fresh copy of your document, stripping away the invisible, bloated revision history caused by repeated digital signing.
Digital signatures preserve earlier versions of a document to ensure authenticity and prove that the file was not tampered with. Repeatedly signing, modifying, or removing signatures creates a chain of these embedded revisions, which vastly inflates the file size.
Simply deleting a signature does not automatically delete this accumulated data. Forcing the PDF editor to write a completely new file is the most effective way to discard unnecessary historical revisions.
Launch your PDF reader or editor and open the oversized signed PDF file.
Navigate to the 'File' menu located in the top-left corner of the application interface.
Click on 'Save As' instead of 'Save'. This is crucial, as a standard 'Save' simply appends changes to the existing bloated file.
Enter a new file name or choose a different save location, then click 'Save' to generate a clean, optimized copy of your document without the hidden revision chain.
Manage and Compress Signed PDFs with WPS Office
WPS Office provides robust PDF tools that allow you to handle digital signatures efficiently and compress overly large PDF files with just a few clicks, ensuring your documents remain easily shareable.
- 1. Open your PDF in WPS Office: Launch WPS Office and open the bloated PDF document you need to optimize.
- 2. Use the Compress Tool: Navigate to the 'Tools' tab on the top ribbon and select the 'Compress PDF' feature.
- 3. Reduce File Size: Select your desired compression level (HD, Normal, or Basic) and click 'Compress' to instantly shrink the file size.
Frequently Asked Questions
Why does a single digital signature add so much data to my PDF?
PKCS#7 signatures often embed certificate chains, revocation information (such as CRL/OCSP), and a complete snapshot of the document's state at the exact time of signing. This guarantees the file hasn't been tampered with but significantly increases the file size.
Does removing a signature automatically reduce the PDF file size?
No, it usually does not. Simply removing a signature often just appends a new revision indicating the removal, leaving the original signed data and document snapshot hidden in the file history. You must use 'Save As' to clear this historical data.
How can I prevent the PDF size from increasing in the future?
Finalize all text, formatting, and annotations before applying any digital signatures. Avoid workflows where the document is repeatedly signed, edited, and re-signed by the same person, as this creates a long chain of embedded revisions.
