How to Edit PDF Files - Free Tools for Manipulating PDF Documents
The PDF file format was originally created by Adobe in the early ’90s and there are now over 450+ million PDF documents on the Internet according to Google. Compare this with the DOC format that was created in early ’80s (much before PDF) but there are only 75 million .doc files on the web today.
via labnol.org
Note that you can't edit a PDF that is password protected, unless you have the password (or can hack it). I didn't realize that there were this many free editors available.
