Why do I get an error message when opening a digitally signed PDF in Acrobat?

Due to an outdated root certificate Adobe Reader may show the error message "At least one signature has problems" when opening a digitally signed PDF.

You can ignore this error message. From a legal perspective it is sufficient if the digital signature check was successful and you archived both the PDF file and the verification report in a digital form, acceptable for auditing purposes.

 

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