[Macpartners] Signing a PDF document with a digital ID?

[Mark London]

Hi - Someone here was given an MIT PDF file to ok a cash advance.  2 
people had to sign.  The 1st person signed on his PC, and claimed he was 
able to use his Kerberos certificate/id.  He doesn't remember exactly 
how he did this.  In any event, the other person is using a MAC, and 
when he clicks on the form entry for a digital id, it prompts him to 
specify a file.  What should he do at this point?  I.e., do we need to 
download his MIT certificate to a file, or is there a way to select the 
certificate, that is already in the keychain?  Thanks. - Mark