Breaking passwords is illegal so I wont touch it...
To edit PDF's you need to get the full version of Acrobat (you probably have Acrobat Reader which is like the Word Viewer software - can see the file but cant edit it). If you dont have it, you can make use of some pdf to word conversion utils that are available, export to word, make corrections/highlights then use word to pdf conversion utilities... All are available on the net and to find freeware stuff, go to
www.nonags.com or similar site and search for pdf...
Arun