About security
Acrobat security is similar to home security. Just as people lock their doors to prevent
others from entering their houses without permission, authors may use the various Acrobat
security features to "lock" PDF documents. For example, authors can add passwords to
restrict users from opening a PDF document, and they can prevent users from printing or
editing a document. They can also use digital signatures to certify and encrypt PDF
documents. A document to which security features have been applied is called a restricted
document.
PDF files can take advantage of the security features of Windows XP and a number of
other security systems:
● Password-protected documents. When you receive a restricted PDF document, you may
need to enter a password to open it.
● Restrictions against copying or printing. Some restricted or certified documents do not
require a password but still prevent you from copying information or printing the file.
● Encrypted documents. If a document is encrypted, you may not be able to open it without
permission from the person who created the document. Documents with special security
policies applied may require you to log in to a server to open the document. If you're
having trouble opening a PDF document, or if you're restricted from using certain
features, contact the PDF document author.
● Digital signatures. If the PDF document contains additional usage rights, you may be
asked to sign or approve a PDF document. (See Signing PDF documents in Adobe
Reader.)
● Documents to which a server-based security policy has been applied. (See Viewing PDF
documents with security policies.)
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