How to resolve “At least one signature has problems.” error in Adobe Reader?

Adobe Reader software is used to open PDF documents. The PDF documents may be encrypted for security. And also PDF documents may be digitally signed for authentication. When there is any digital signature required to authenticate the PDF documents are not available on your system or the signature has problems, Adobe Reader fails to authenticate the document, and will display the “At least one signature has problems” message. The below steps explains how to resolve this issue.

Step 1. Open your PDF document in the Adobe Reader application. If there is a signature problem with the document, it will show the message “At least one signature has problems” message.

Step 2. Click on the “Signature Panel” button which will be on the right of the message.

Step 3. Click on Validate All link. It will prompt the message to validate all signatures depending on the settings.

Step 4. Click on the OK button to validate all the signatures. Once all the signatures are validated it will show a success message depending on the settings.

Step 5. If the signatures are successfully validated; Adobe Reader, will show the “Signed and all signatures are valid.” message. Then, you can skip the next steps.

If you are still seeing the “At least one signature has problems” message, proceed with the next steps.

Step 6. Select the signature which has the problem and right-click on it. It will display a pull-down menu.

From the pull-down menu, select the “Show Signature Properties…” menu item. Adobe Reader will display the Signature Properties window.

Step 7. Click on the “Show Certificate…” button. It will open the Certificate Viewer window to view the details of a certificate.

Step 8. From the Certificate Viewer window, click on the Trust tab. It will display “Trust Settings” and “This certificate is not trusted” messages.

Step 9. If you received the PDF document from a trusted source or the certificate is from a trusted source, click on the “Add to Trusted Identities…” button. Otherwise, skip here and don’t validate your signatures.

Step 10. Adobe Reader, will prompt you a message “Trusting certificates directly from a document is usually unwise. Are you sure you want to do this?”. Click on the OK button if you trust the source. Otherwise, stop to continue to the next steps.

Step 11. Now it will display the “Import Contact Setting” window. Select the “Use this certificate as a trusted root“ check box and click on the OK button to import contact settings into your system.

Step 12. Now the signature is validated and it will display Signature is VALID, signed by message in Signature Properties window which is opened in Step 6.

Step 13. Click on the Close button to close the Signature Properties window.

Now the signature is trusted and validated. Once it is validated it will display a “Signed and all signatures are valid.” message. Now the PDF document is validated.