Quit Acrobat or Acrobat Reader application.
A digital certificate chain is made up of a list of certificates that start from a root certificate issued by a certifying authority and terminates with the End Entity (EE) certificate. For validation, your End Entity certificate (EE), Intermediate certificate Authority (ICA), or Root CA has to be part of the trusted list. Acrobat or Acrobat Reader tries to validate the signature by checking the certificate chain.
With the September 2021 release of Acrobat or Acrobat Reader (version 2021.007.20091 and later), the digital signature status is not shown as invalid or unknown when an exception occurs during the processing of a certificate chain.
To revert to the previous behavior in which Acrobat or Acrobat Reader quits processing the remaining chains and returns the signature status as invalid or unknown, modify the bADC4326651 registry key or the plist file value and set it to 1 in the following location:
You can create a bADC4326651 registry key on Windows or the corresponding key on a plist file on macOS, and choose if you want Acrobat or Acrobat Reader to display the warning message when an exception occurs while validating the certificate chain, or trust the certificate and display no error.
In the registry editor, based on your installed version of the product, go to the version-specific location listed below, and modify or create the DWORD (32-bit) key bADC4326651 at the location,
When an exception occurs during the processing of a certificate chain, Acrobat or Acrobat Reader quits processing the remaining chains and returns the signature status as invalid or unknown.