User manual

About security
Acrobat security is similar to home security. Just as you lock your doors to prevent
someone from entering your house without permission, you use Acrobat security features
to lock a PDF document. For example, you can use passwords to restrict users from
opening, printing, and editing PDF documents. You can use digital signatures to certify
PDF documents, and you can encrypt PDF documents so that only an approved list of
users can open them. If you want to save security settings for later use, you can create a
security policy that stores security settings. For an overview of the different types of
security, see Viewing the security settings of an open Adobe PDF document.
Acrobat takes advantage of the security features of Windows XP and a number of other
security systems:
● For password protection, Acrobat supports 128-bit RC4 and 128-bit AES (Advanced
Encryption Standard) security methods. You can choose which method to use when
securing documents.
● For digital signatures and document encryption, Acrobat supports public-key
cryptography. Public-key cryptography uses two keys: a public key, which is stored inside
a certificate that can be shared with other users, and a private key, called a digital ID,
which you do not share with others. The public key certificate is used to encrypt
(scramble) documents or to verify digital signatures, and the digital ID is used to decrypt
(unscramble) encrypted documents or to create digital signatures. (See Using digital IDs
and certification methods.)
Note: "Security" is sometimes confused with "accessibility," which involves making
documents for the visually impaired easier to read. For details on accessibility, see
Making existing Adobe PDF documents accessible.