The PDF Password Recovery software can be used to decrypt protected Adobe Acrobat PDF files, which have "owner" password set, preventing the file from editing (changing), printing, selecting text and graphics (and copying them into the Clipboard), or adding/changing annotations and form fields.
Decryption is being done instantly. Decrypted file can be opened in any PDF viewer (e.g. Adobe Acrobat Reader) without any restrictions -- i.e. with edit/copy/print functions enabled. All versions of Adobe Acrobat (including 5.x 6.x 7.x , which features 48-bit,128-bit and AES encryption) are supported.
The standard security provided by PDF consists of two different methods and two different passwords.
A PDF document may be protected by password for opening ('user' password) and the document may also specify operations that should be restricted even when the document is decrypted: printing; copying text and graphics out of the document; modifying the document; and adding or modifying text notes and AcroForm fields (using 'owner' password). (command line)
OK, so you want to stamp your document. Maybe you need to give reviewers some advice about the document's status or sensitivity. This tip from author Ted Padova demonstrates how to add stamps with the Stamp Tool along with related comments.