Error during signature verification. Adobe Acrobat error. Bad parameter. Sign
When signing a PDF document and loading signed PDF into Acrobat Reader DC (v2022.001.20085, 64 bit). The file will load correctly but when clicking on on the signature it will give the error:
Error during signature verification. Adobe Acrobat error. Bad parameter.
After a LOT of trail and error I found out why. This is because Acrobat does not follow the spec in some cases. This why some validation works correctly in some parts, but not others.
The field type (FT) shall be Sig, and the field value (V), if present,
shall be a signature dictionary containing the signature and specifying various attributes of the signature field
(see Table 252).
Source: PDF 32000-1:2008
V should be a
Dictionary according to this. But when a direct Dictionary is used you get the error above. When you use a Reference to a new object that is a Dictionary it works.
V = Dictionary -> Error: Bad parameter
V = Reference pointing to Dictionary Object -> Ok
I think this should be fixed and Acrobat should allow both References and direct a Dictionary.
For more info: https://stackoverflow.com/questions/72477325/pdf-digital-signature-has-bad-parameter-in-acrobat