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Issue
I received a PDF that has a banner at the top saying, "At least one signature is invalid". How do I fix this error?
Explanation
When opening a digitally signed PDF, Adobe may display a message indicating that ”At least one signature is invalid". This message typically appears when Adobe does not recognize the certificate authority that issued the digital certificate used to sign the document. For UTD-signed documents, this may occur if the signer used a UTD-issued certificate that isn’t automatically recognized by Adobe.
As the recipient of a PDF signed with a UTD-issued certificate, you may need to manually “trust” UTD’s main certificate in Adobe. By doing this, you allow Adobe to validate the certificate chain, recognizing UTD as a trusted authority and ensuring the document signature appears as valid.
For a step-by-step guide on how to add and trust certificates in Adobe, please follow the instructions provided below or refer to Adobe’s official support documentation.
Trust the Certificate
- Click the Signature Panel button in the banner where the error is.
- Then, click on the Signatures iconin the left-hand sidebar.
- You will be able to see all the signatures which are causing the issue. However, you need to validate only one signature to remove this error.
- To do that, expand a signature and then the Signature Details section by clicking the arrows adjacent to them. Then, select Certificate Details.
- Select the row above the one with a warning sign in the new window. The row should state "The University of Texas at Dallas RSA".
- In the window, navigate to the Trust tab and select Add to Trusted Certificates.
- Select OK in the first dialog box after reading the instructions displayed.
- In the Import Contact Settings window which opens next, check the option "Use this certificate as a trusted root".
- Select OK to close all windows and finish the task.
- Close the document and reopen it. You should not get the error again.