How to Fix DigiCert PDF Signature Validity Unknown in Adobe Reader
Question details
The user needs to resolve an issue where a valid DigiCert digital signature shows up as "validity unknown" when a document is opened.
- Product
- Adobe Reader
- Device & OS
- not provided
- Scenario
- Verifying the authenticity of a digitally signed PDF document.
- Observed behavior
- Adobe Reader displays an "unknown signer" or "validity unknown" warning because it cannot automatically establish a trusted certificate chain for the DigiCert signature.
Ensure you have the latest version of your PDF reader installed and have downloaded the official DigiCert Global Root certificate file from the DigiCert website to your local storage.
Add the DigiCert Root Certificate to Trusted Identities
Manually importing the DigiCert root certificate ensures the PDF software explicitly trusts signatures issued by this authority.
PDF readers rely on a specific list of trusted certificates to validate digital signatures. If the DigiCert root certificate is missing from this internal list, perfectly valid signatures will trigger an error warning.
Launch Adobe Reader and navigate to 'Edit' > 'Preferences' on Windows, or 'Acrobat Reader' > 'Preferences' on Mac.
Select 'Signatures' from the Categories list on the left side of the window, then click the 'More' button under the 'Identities & Trusted Certificates' section.
Select 'Trusted Certificates' on the left menu, click 'Import', and browse your computer to locate the DigiCert Global Root certificate you previously downloaded.
Click on the newly imported certificate in the list, click the 'Edit Trust' button, and check the box that says 'Use this certificate as a trusted root'.
Update the Approved Trust List Automatically
Updating the trust list fetches the latest trusted certificates approved by the software provider, automatically resolving missing root certificate issues.
Easily Manage and Validate PDF Signatures with WPS Office
Avoid complex certificate management by using WPS Office. Our built-in PDF reader provides a lightweight, secure, and user-friendly environment to view, sign, and verify PDF documents without the hassle.
- 1. Download and Install: Install WPS Office for free from the official website and open the application.
- 2. Open Your PDF: Drag and drop your digitally signed PDF document directly into the WPS Office workspace.
- 3. View Signatures: Navigate to the 'Protect' tab to manage, verify, and view digital signatures securely within your document.
Frequently Asked Questions
Why does a perfectly valid digital signature show as 'unknown'?
This happens when your PDF reader cannot establish a chain of trust to the root certificate authority (like DigiCert) that issued the digital ID. The software needs to have the corresponding root certificate stored in its trusted list to confirm the signature's authenticity.
Is my PDF document compromised if the signature validity is unknown?
Not necessarily. An 'unknown' validity simply means the PDF software hasn't verified the certificate chain locally. The document's integrity and content might still be completely intact, but you must add the trusted root certificate to technically confirm it.
Where can I safely download the DigiCert Global Root certificate?
You can download official root certificates directly from the DigiCert Trusted Root Authority Certificates page on their official website. Always ensure you download security certificates directly from the official provider to avoid security risks.
Can I validate signatures automatically without manual imports?
Yes, by enabling automatic trust list updates in your software's Trust Manager preferences, the PDF reader will periodically connect to its server to download updated trusted root certificates, automating the validation process.
