How to Troubleshoot an Untrusted Digital Signature Certificate in PDF
Question details
The user needs to understand why a PDF application reports a digital certificate as not trusted and how to manage trust settings to validate the signature.
- Product
- Adobe Acrobat
- Device & OS
- not provided
- Scenario
- Verifying or applying a digital signature to a PDF document.
- Observed behavior
- The application displays a warning that the digital certificate is untrusted, or the software hangs when attempting to open the signature selection window.
Before modifying certificate trust settings, ensure you know the identity of the document sender and can verify the issuing authority of the digital certificate. Modifying trust settings for unknown certificates can pose security risks to your system.
Review and Manually Trust the Certificate
If you are certain the certificate is from a reliable source, you can manually add it to your trusted certificates list to clear the untrusted warning.
Digital signatures are often marked as untrusted if the root certificate of the issuer is not pre-installed in your system's or application's trust store. You can manually inspect and trust the certificate if you have verified its origin.
Open the PDF document and click on the 'Signature Panel' or click directly on the signature block that displays the warning. Select 'Signature Properties' from the context menu.
Click the 'Show Signer's Certificate' button to review the issuing authority, validity period, and intended usage.
In the certificate viewer window, click on the 'Trust' tab located at the top.
Click the 'Add to Trusted Certificates' button and confirm any security prompts that appear.
Check the boxes for the specific actions you want to trust (such as 'Use this certificate as a trusted root') and click 'OK' to apply the changes.
Fix Application Freezing During Signature Selection
Resolve issues where the PDF reader hangs or fails to open the signature window when attempting to sign a document.
Easily Sign and Secure PDFs with WPS Office
WPS Office provides a streamlined, secure environment for adding and managing digital signatures in PDF documents. Bypass complex trust configuration errors with our intuitive PDF tools designed for smooth document workflows.
- 1. Open the PDF: Launch WPS Office and open the PDF document that requires a digital signature.
- 2. Navigate to the Protect Tab: Click on the 'Protect' tab located on the top ribbon menu.
- 3. Select Sign Document: Click 'Sign Document' to either create a new digital certificate or import your existing one.
- 4. Apply and Save: Place the signature in the desired location on the page and save your securely signed PDF.
Frequently Asked Questions
Why does a digital certificate expire?
Digital certificates have an expiration date set by the Certificate Authority (CA) to maintain security standards. Once expired, the certificate must be renewed or a new one generated to ensure the cryptographic keys remain safe from vulnerabilities.
Can I remove a certificate from my trusted list later?
Yes. In most PDF applications, you can go to the application preferences, navigate to the 'Signatures' or 'Trust Manager' section, and view your trusted identities. From there, you can remove or edit previously trusted certificates.
What should I do if the certificate issuer is unknown?
Do not add it to your trusted list. Contact the sender through an alternative communication channel (like a phone call or a separate email) to verify the document's authenticity and ask them about the certificate issuer before taking any action.
Why does the signature show as valid on another computer but untrusted on mine?
Certificate trust is often managed locally on each machine. The other computer might have the specific root certificate installed in its system trust store or application preferences, whereas your computer does not.
