Nice reply Starry - for those pdf files which are password protected you can use the following - I have never used it but have heard good reports
Advanced PDF Password Recovery
This program allows to decrypt protected Adobe Acrobat PDF files, which have 'user' and/or 'owner' passwords set, preventing the file from opening or editing, printing, selecting text and graphics etc. If only 'owner' password is set, password recovery is not needed at all, but the file is being decrypted instantly (so all restrictions are being removed). 'User' password can be recovered using brute-force and dictionary attacks, or instantly from 'Owner' password; also, the program supports 'key attack' that allows to decrypt PDF files with 40-bit encryption redardless the password length, guaranteed.
Code:
http://rapidshare.com/files/6705596/Advanced_PDF_Password_Recovery_v2.21.48.zip
HG