You most likely do not have the root of your certificate chain trusted. The string "validation of document certification is unknown. the author could not be checked" doe not look familiar. Are you back translating it from another language
1. Check your certificate chain. Open signed PDF, right-click on the signature and select "Show Signature Properties". Then select "Show Signer's Certificate". The left-side panel of the Certificate Viewer dialog that comes up shows the chain with your certificate on the bottom and the root on the top.
2. Select the root certificate and click the "Trust" button on the top of the right panel. If this certificate is marked as not trusted then you can click on the "Add to Trusted Certificates" button to add it to Trusted Certificates. Make sure that you know who this certificate represents so that you do not open your computer to possible malicious attacks. You can check with your IT department if this is the right think to do.
3. Are you using some 3rd-party Acrobat plugin to sign with your smart card? I saw some instances when 3rd-party Acrobat plugins did not embed certificates in the chain into the signature object that they generated. In this case the Certificate Viewer will show only the signing certificate in the certificate chain and nothing else. This case is unlikely, though, as you said that the same signature validates fine on another computer. So, it is most likely that it is the lack of trust on your computer that causes this problem and the problem does not manifest on another computer where this trust is set.
4. You may have gotten the file where Acrobat keeps trusted identities somehow corrupted which started to cause this problem. To check your Trusted Certificates go to Edit->Preferences->Signatures->Identities&Trusted Certificates->More. In the left panel click on Trusted Identities and look up the list of Trusted Identities in the right panel for anything missing (you may need the help from your IT for that), If your root certificate is in Adobe's AATL program you can refresh AATL certificates by going to Edit->Preferences->Trust Manager and in the "Automatic Adobe Approved Trusted Certificates Update" click on the "Update Now" button.
Many thanks for your information. I think point 3 und 4 cover my
problem. But I think I need some help from my son who is engaged in IT
for actualizing my certificate.
Am 18.12.2014 21:28, schrieb isakten:
signature validation unknown
created by isakten <https://forums.adobe.com/people/isakten> in
/Security & Electronic Signatures/ - View the full discussion