It seems that those errors with errocode 0x2711 or 0x20C occur if a digital signature embedded in the pdf document is using either ECC as signature algorithm or PSS padding.
This let me assume that Adobes signature verification routine cannot handle elliptic curves or if using RSA as signature algorithm the newer PSS/RSAPSS padding scheme.
But I only get the error mentioned by you if I try to validate signatures using ECC.
When verifying a signature using with PSS padding the signature is verified as invalid. The given reason is the use of an unknown format in digital signature. So the pss padding could be the unknown format.
Unfortunatly the people think the signature is invalid. But actually it is not. Same with the internal cryptographic library error. It is just that Adobe cannot handle those signatures. So I would recommend the use of software built for signature verification.