management-trusted-certificates

Managing trusted certificates in Adobe Reader

When opening a signed PDF, Adobe Reader prompts “At least one signature requires validating” or “at least one signature has problems” in the signature panel and in the signature stamps (if any). This means that Adobe does not trust the Certificate Authority that issued the certificate, eg., FNMT Camerfirma, Firmaprofesional, AVANSI, etc)

PDF document with error message

To solve this, configure Adobe Reader to trust the certificate issuer. Right-click on the signature which is causing problems and select “Show signature properties”.

Show signature properties to trust the certificate issuer

A new window opens with the ”Signature properties”. Here are the details on the signature. Click on “Show signer’s certificate”.

Signature Properties to show signer's certificate

Next, the Certificate Viewer opens. We see the certificate issuer (in this case Avansi) and the certificate details.

Certificate VIewer showing  Certifcate Authority

We open the “Trust” tab, where we see that This certificate is not trusted . Click on “Add to trusted certificates“.

Certificate Viewer to add trusted certificate

Adobe Acrobat may show a warning message after clicking the button above. Click “OK”.

Adobe Acrobat Security message

The import contact settings window will be open. By default, the option “Use this certificate as a trusted root” is selected in the Trust tab. Keep this option selected and click OK in the following windows.

Import Contact settings with certificate details

Go back to the Signature Properties window. Press “Validate Signature”.

Validate Signature to trust the signer's identity

Perfect! Adobe Reader already confirms that the signature is valid as it already recognizes all certificates from the trusted issuer. Please do this operation with all Certificate Authorities

The signature is now valid
PDF document with valid signatures