Adobe Acrobat XI - Manual (Page 364)

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Security
Last updated 1/14/2015
8 Select an Acrobat version from the Compatibility menu. Choose a version equal to or lower than the recipients’
version of Acrobat or Reader. The Compatibility option you choose determines the type of encryption used. It is
important to choose a version compatible with the recipient's version of Acrobat or Reader. For example, Acrobat 7
cannot open a PDF encrypted for Acrobat X and later.
• Acrobat 6.0 And Later (PDF 1.5) encrypts the document using 128-bit RC4.
• Acrobat 7.0 And Later (PDF 1.6) encrypts the document using the AES encryption algorithm with a 128-bit key
size.
• Acrobat X And Later (PDF 1.7) encrypts the document using 256-bit AES. To apply 256-bit AES encryption to
documents created in Acrobat 8 and 9, select Acrobat X And Later.
9 Select what you want to encrypt:
Encrypt All Document Contents Encrypts the document and the document metadata. If this option is selected,
search engines cannot access the document metadata.
Encrypt All Document Contents Except Metadata Encrypts the contents of a document but still allows search
engines access to the document metadata.
Note: The iFilter and the Find or Advance Search commands of Acrobat do not look into the PDF’s metadata even when
you select the Encrypt All Document Contents Except Metadata option. You can use a search tool that takes
advantage of XMP metadata.
Encrypt Only File Attachments Requires a password to open file attachments. Users can open the document without
a password. Use this option to create security envelopes.
10 Click OK. At the prompt to confirm the password, retype the appropriate password in the box and click OK.
Note: If you forget a password, you cannot recover it from the PDF. Consider keeping a backup copy of the PDF that isn’t
password-protected.
Remove password security
You can remove security from an open PDF if you have the permissions to do so. If the PDF is secured with a server-
based security policy, only the policy author or a server administrator can change it.
1 Open the PDF, then select Tools > Protection > Encrypt > Remove Security.
2 Your options vary depending on the type of password security attached to the document:
• If the document had only a Document Open password, click OK to remove it from the document.
• If the document had a permissions password, type it in the Enter Password box, and then click OK. Click OK
again to confirm the action.