Fix Digital Signature Adding Several Megabytes to PDF File Size
Question details
The user experiences a significant file size increase of about 3 MB when applying a digital signature to a PDF using a USB token on a specific Windows 10 computer, unlike on other devices.
- Product
- PDF Editor
- Device & OS
- Windows 10
- Scenario
- Applying a digital signature to a PDF document using a certificate and USB token.
- Observed behavior
- The PDF file size inexplicably increases by several megabytes after signing on one computer, whereas the same operation on other computers results in little to no file size increase.
Before proceeding, check if your organization requires Long-Term Validation (LTV) for digital signatures, as disabling certain revocation data to save space may affect compliance.
Adjust PDF Application Signing Preferences
Modify your PDF reader's digital signature settings to manage embedded certificate chains and revocation data, which are the most common causes of file bloat.
PDF applications often embed Certificate Revocation Lists (CRLs) or Online Certificate Status Protocol (OCSP) responses to ensure the signature remains valid offline. This data can add several megabytes to the document.
Launch your PDF application and navigate to the 'Edit' menu, then select 'Preferences' (or press Ctrl+K).
In the left-hand panel, click on 'Signatures' or 'Security'.
Under the 'Creation & Appearance' section, click the 'More' button to access advanced signing preferences.
Uncheck options related to 'Include revocation status' or 'Embed certificate chain' if your security policy permits it, then click 'OK' to save.
Update Token Middleware and Software
Ensure your USB token drivers and PDF application are fully updated to prevent software glitches from causing excessive file bloat.
Sign PDFs Efficiently with WPS Office
WPS Office offers a fast, lightweight PDF reader and editor that allows you to easily manage digital signatures without unnecessary file size bloat. It provides a secure, streamlined way to sign documents while maintaining optimal performance and compatibility.
- 1. Open Your PDF: Launch WPS Office and open the PDF document you need to sign.
- 2. Navigate to the Protect Tab: Click on the 'Protect' tab located in the top menu ribbon.
- 3. Select Digital Signature: Click on 'Sign' or 'Digital Signature' to select your certificate.
- 4. Apply Signature: Drag to place the signature field on your document, apply your certificate, and save the file securely.
Frequently Asked Questions
Why does my PDF file size increase so much when I digitally sign it?
The file size usually increases because the PDF software embeds the entire certificate chain and Certificate Revocation List (CRL) data. This is done to ensure the signature can be verified offline in the future, known as Long-Term Validation (LTV).
Can I compress a digitally signed PDF to reduce its size?
No, compressing or altering a digitally signed PDF will invalidate the existing signature because it changes the document's underlying data. You should use a PDF optimizer to compress the file before adding the digital signature.
What is Long-Term Validation (LTV) and does it affect file size?
LTV is a feature that includes all necessary revocation data and timestamps within the PDF at the time of signing. While it guarantees the signature remains verifiable long after the digital certificate expires, the embedded data significantly increases the file size.
