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Adobe Acrobat Help
Digitally Signing PDF Files
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4
Click OK.
About Acrobat Self-Sign Security
Acrobat Self-Sign Security, the default Acrobat signature handler, provides a quick and
easy method of signing documents using a private/public key (PPK) system to verify the
authenticity of signatures and the integrity of signed document versions. (This is a direct-
trust system.) You can also use Acrobat Self-Sign Security to encrypt PDF files, as described
in
“Encrypting PDF files” on page 192
.
In Acrobat Self-Sign Security, each signature is associated with a profile that contains
unique security data—a private key and a public key. The private key is a password-
protected numerical value that allows the user to sign a document. The
public key
is
embedded in the digital signature and is used to mathematically verify digital signatures
when the signatures are verified.The private key encrypts a checksum that is stored with a
signature when you sign; the public key decrypts the checksum when you verify. (Acrobat
Self-Sign Security uses the RSA algorithm for generating private/public key pairs and the
X.509 standard for certificates.)
Because other users must have access to your public key to verify your signature, your
public key is contained in a
certificate
that can be shared. (See
“Managing user certificates”
on page 205
.) This system of sharing certificates used by Acrobat Self-Sign Security is
referred to as
direct-trust
, which means that you share directly with other users rather than
going through a third-party agent.
Note:
Acrobat Self-Sign Security does not include a public-key infrastructure with third-
party certification and is not intended to serve all signing purposes. See the Security folder
on the Acrobat CD or the Adobe Web site (www.adobe.com) for information on signature
handlers with more advanced features.
Setting up profiles in Acrobat Self-Sign Security
Before you can sign documents with Acrobat Self-Sign Security, you must set up a
profile—a password-protected file—containing your name, your password, and other
basic attributes. You may want to create more than one profile if you sign documents in
different roles.
Creating profiles
Your profile file stores your private key (encrypted), your public key (wrapped in a certif-
icate), your list of trusted certificates (certificates of other users), and a time-out value
representing when a password is required for signing. The name of the file is the profile
name you provide, plus the extension .apf.
Important:
Always make a backup copy of your profile file. If your profile file is lost or
corrupted, or if you forget your password, you cannot add or verify signatures with that
profile. (See
“Backing up your profiles” on page 198
.)
To create a profile:
1
Assuming you are not already logged in to a profile, do one of the following:
•
Choose Tools > Self-Sign Security > Log In.
•
Choose Tools > Digital Signatures > Sign Document. Click OK in the Digital Signatures
Alert dialog box, and drag on the page to create a signature box.