How to Fix Invalid PDF Digital Signatures on One Computer
Question details
The user needs to resolve an issue where a PDF digital signature validates successfully on one computer but appears as invalid or unverified when opened on a different computer.
- Product
- PDF Editor / Adobe Acrobat
- Device & OS
- not provided
- Scenario
- Viewing and validating a digitally signed PDF document across multiple devices.
- Observed behavior
- The PDF signature and certificate show as valid on the original computer, but display an invalid or unknown trust error when opened on a second computer.
Ensure that the computer showing the error is connected to the internet to perform background certificate revocation checks, and verify that the system date and time are accurate.
Update PDF Software and Configure Trusted Certificates
Updating your PDF reader and manually trusting the signer's certificate ensures local validation matches the original computer's trust settings.
Certificate trust configurations are stored locally on each computer. Because of this, copying a valid PDF file to a new machine does not transfer the local trust settings. You must manually add the certificate to the new computer's trusted list.
Open your PDF application, navigate to the Help menu, and select Check for Updates to ensure you are running the latest version.
Open the digitally signed PDF and click on the Signature Panel on the left side of the screen to view the validation status.
Right-click the signature that displays as invalid, select Show Signature Properties, and then click on Show Signer's Certificate.
Navigate to the Trust tab and click Add to Trusted Certificates. Only perform this step if you have personally verified the sender's identity.
Click OK to apply the settings, then click Validate Signature in the properties window to refresh the document's security status.
Reset PDF Application Preferences
Resetting the application preferences can resolve corrupted local security settings or cache issues preventing signature validation.
Easily Validate and Sign PDFs with WPS Office
WPS Office provides a seamless and secure environment to view, validate, and apply digital signatures to your PDF documents. It offers a lightweight, cross-platform solution with intuitive security management.
- 1. Open the PDF: Launch WPS Office and open your digitally signed PDF document.
- 2. Access the Protect Tab: Navigate to the 'Protect' tab on the top ribbon menu to access security and signature tools.
- 3. Manage Signatures: Click on 'Validate Signatures' to let WPS Office automatically check the certificate trust and validation status of the document.
Frequently Asked Questions
Why does my PDF signature say 'At least one signature has problems'?
This usually occurs when the PDF software cannot verify the signer's identity. It happens if the root certificate is not in your computer's local list of trusted identities, or if the document was modified after the signature was applied.
Does copying a PDF to another computer break the digital signature?
No, the signature itself remains intact within the file. However, the new computer must independently verify the certificate. If it lacks the necessary trusted certificates or internet access for revocation checks, it will display a validation error.
How does the computer's date and time affect PDF signatures?
Digital certificates rely on valid timestamps to confirm they haven't expired. If your computer's clock is set incorrectly, the software may wrongly determine that the certificate has already expired or is not yet valid.
What are Certificate Revocation Lists (CRLs)?
CRLs are lists maintained by certificate authorities that identify certificates that have been revoked before their scheduled expiration date. Your PDF software checks these lists to ensure the signature is still trustworthy.
