Adobe ACROBAT READER 7.0 Manual page 151

About digital IDs and certification methods
PDF authors can use Acrobat to let users sign a PDF document whether they use Adobe
Acrobat or Adobe Reader. If you open a PDF document with additional usage rights, you
can add a digital signature, which requires that you use a digital ID. If a PDF document
does not have additional usage rights, you cannot use digital IDs or add signatures. (See
About Adobe PDF documents with additional usage
A digital ID lets you create digital signatures. Digital IDs are also referred to as private
keys, credentials or profiles. You can get a digital ID from a third-party provider, or you
can create a self-signed digital ID and share your signature information with others. A
certificate is a confirmation of your digital ID and contains information used to protect
data. (See Managing digital ID
Related Subtopics:
Obtaining a digital ID from a third party
Creating digital IDs
Finding and adding existing digital IDs
Selecting digital IDs
Using third-party digital IDs
certificates.)
rights.)