I already written about howto remove a password from all PDF files under Ubuntu or any other Linux distribution in a batch mode. However, many user want a simple command to recover password from pdf files. This is useful if you forgotten your password for pdf file. It is also useful for data-archaeologists, computer forensics professionals, people who want to test their password-strength (pdf files generated by webpass) and many more.
Forensics is the art and science of applying computer science to aid the legal process.
Mihai Criveti has published a list for digital forensics work. This page is worth bookmark:
Computer Forensics is a science and an art. And to perform it, you need tools to identify, acquisition, preserve and analyze data in a clean, safe, non-destructive manner. Lots of tools. Everything from data acquisition to virtualization and steganalysis.
A list of more or less free tools (mostly open source or freeware, but I have included some relevant commercial products) no digital forensics expert should be without
=> Digital Forensic Tools: Imaging, Virtualization, Cryptanalysis, Steganalysis, Data Recovery, Reverse Engineering