you want to authenticate the identity of a user and the document's
content, add a signature field to the form. A digital signature
stores information about the signing party and the state of the
document when it is signed. Adobe signatures support the Public
Key Cryptography Standard (PKCS) #7, using the RSA MD5, RSA SHA-1,
or DSA SHA-1 hash algorithm.
You can specify whether a signature covers an entire form or
a collection of objects in a form. If you want the signature to
apply to a collection of objects, the signing party must use Acrobat
or Adobe Reader version 8.0 or later.
If the signature covers a collection of objects, the fields are
locked and cannot be modified after the document is signed. The
lock is inherited. For example, when a subform is locked, all the
objects in the subform inherit the lock.
To sign the form, the user clicks the signature field. For more
information about signing PDF forms in Acrobat, see Acrobat Help.
The signature field does not generate a digital signature directly.
It invokes a third-party signature handler through scripting, and
the signature handler provides the required digital signature functionality.
Users cannot sign forms without an appropriate signature handler.
If required, you can change the signature field name in the Hierarchy
palette after you add the object to the form design.
After you add a signature field to the form design, you can define
the signature properties in the Signature tab of the Object palette.
You can define whether the signature covers the entire form or a
collection of field objects and specify default signature properties.
You can edit the caption text and manipulate the object’s properties
in the Field tab of the Object palette. You can define these properties: