Certificate Signatures

Adobe Acrobat supports the use of certificate signatures (also known as digital signatures), which let you sign PDF files with a certificate-based digital ID. This certificate ID is issued by a trusted third-part certificate authority, such as CAcert.org or VeriSign.

A digital signature can be used to authenticate the identity of a user and the document’s content. It stores information about the signer and the state of the document when it was signed. Any subsequent changes to a signed PDF file invalidate the signature.

The AFP2PDF Plus Transform requires a digital certificate in the PKCS#12 format. PKCS stands for Public Key Cryptography Standard, originally developed by RSA Security, Inc. PKCS#12 defines a file format used to store private keys with accompanying public key certificates, protected with a password-based symmetric key.

The AFP2PDF Plus Transform makes use of a digital certificate through the use of one of these options in the a2pxopts.cfg file:

  • Certificate requires both the name of the PKCS#12 file and its password to read the PKCS#12 file.

  • Certificate2 requires the name of the PKCS#12 file, but lets you point to a file that contains the needed password.

Once the file has been signed, the validity can be checked by opening the file with Adobe Acrobat.