I have a government-issued ID card, that I am trying to use to sign a PDF document using Adobe Reader XI on a Windows 7 machine. The digital ID for the smart card shows up in Preferences > Signatures > Identities and Trusted Certificates, with these characteristics as the intended usage: Digital Signature, Client Authorization. When I try to sign the document, however, that ID does not show up as an option. I have a card reader attached to my computer, which seems to be reading the smart card fine, but if I try to create a new ID, using the option 'A device connected to this computer', I get an error that says "Acrobat could not find any new digital IDs. If your digital ID is on a hardware token, please make sure it is plugged in and the token interface is properly configured. Contact your system administrator for further assistance." Any idea on how to use this smart card for a digital signature, or if it is not possible, why not?
Sabian Zildjian pointed you to the right place. Certificates with Client Authorization but not with Email Protection and a few more may not be used for signing PDFs per standards. Before version 11.0.9, I think, Acrobat violated this rule, Many other signing apps (Word) still do.