If you want to open a PDF file which is password protected then for this purpose you can use a freeware utility PDF crack[Developer site].It is available for download in ZIP format.Download it here .Then extract it.This freeware is a small EXE file after executing it from cmd prompt it will show you some options ,then use that accordingly.The default command is pdfcrack.exe -f filename OPTIONS. Cracking a file called abc.pdf without options would be possible with the command pdfcrack.exe -f abc.pdf
The options can be used to load a dictionary file, specify a minimum and maximum length for the password, permutating passwords (currently only uppercase for first letter) or use only the characters specified in a given string as chars for the password. I tried it for my mobile bill PDF file which was password protected.
It provide me the exact password for the PDF file while i was using Adobe reader 7.You can see the snapshot for the commands i performed for retrieving the password of my PDF file.
So it is great password cracking , recovering utility for Adobe PDF files which are password protected.
