I was inspired by the post at Digital Inspiration which was entitled How to Open Password Protected or Encrypted Adobe PDF Files but only mentioned two programs that were both commercial and no mentioning of free PDF Password Recovery tools. And so began my search for a software that would recover the password for a password protected PDF document.
I did find PDF Crack 0.8 for Windows which is a port of the Linux program PDF Crack. PDF Crack is a command line utility which has been tested with Adobe Reader 7 only. It seems that the project has been discontinued and I had no chance to test if with a PDF document that was created and password protected with Adobe PDF 8. If any of you have the chance to create such a document let me know, I would really like to find out if it is possible to recover those passwords as well.
Run pdfcrack.exe in the command line to receive a list of commands. 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.
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Nice article. Is it of practical relevance? Probably not.
How long does it take to crack anything else but an idiot password? Any relevant info here?
I tested, and it does work with Acrobat 8 (PDF 1.7) files. As for recovery time … can take a while with a longer password via brute force attack. If you use a dictionary file, it’s probably faster.
PDFCRACK 0.11 already released, for detail, please visit
http://rubypdf.com/softwares/pdfcrack
btw, after got password, you can use pdfcrypt to remove it.