Adobe ACROBAT READER 7.0 Manual page 157

Managing digital ID certificates
A digital ID certificate contains a public key that is used to validate digital signatures and
to encrypt documents in Adobe Acrobat. You cannot encrypt documents in Adobe Reader.
Before other users can validate your signature on documents they receive, they must have
access to your certificate, which you can share with them. Likewise, other users can share
their certificates with you so that you can build a list of trusted user certificates, called
trusted identities, for validating signatures. (See
Adobe Reader keeps track of the trusted identities that you build. You can also configure
Windows Certificate Security to trust identities in the common Windows Certificate Store.
(See Setting Digital Signature
using other methods, or these validation methods may be integrated with Adobe Reader.
Related Subtopics:
Sharing your digital ID certificate
Building a list of trusted identities
Checking information on certificates
Determining the trust level of a certificate
Configuring identity search directories
Validating
preferences.) Third-party providers may validate identities
signatures.)