According to Wikipedia, retrieved 16:24, 14 September 2011 (CEST), “Portable Document Format (PDF) is an open standard for document exchange. This file format created by Adobe Systems in 1993 is used for representing documents in a manner independent of application software, hardware, and operating systems. Each PDF file encapsulates a complete description of a fixed-layout flat document, including the text, fonts, graphics, and other information needed to display it.”
1 Security and usage rights
A PDF file may be encrypted for security, or digitally signed for authentication.
Various usage rights, can be included, e.g.
- The ability to edit
- the ability to save a PDF document along with annoations or filled-in forms
There exist software for password removal both commercial and free, e.g. pdfcrack under Linux. It takes a long time to break if you don't have a clue what kind of password you used
sudo aptitude install pdfcrack
Example that would permutate assci letters starting at words of 5 letters.
pdfcrack -f test.pdf -n 4 -c abcdefghijklmnopqrstuvwxyz
- Portable Document Format (Wikipedia)
- Adobe Acrobat Reader
- (Some) ebook tools and readers, e.g. calibre
- Ghostview (?)
- evince (PDF/PS viewer, default Ubuntu client ?)
- web services
- Adobe Acrobat Professional
- pdfedit (Linux)
- gpdftext (Linux, for writing e-books)
- Password removal