I haven't tried this yet, but I have just seen a free PDF editor on SourceForge.net
Here's what it says; "Free editor for PDF documents. Complete editing of PDF documents is possible with PDFedit. You can change raw pdf objects (for advanced users) or use many gui functions."
Sounds pretty handy. I would also recommend keeping an eye on and having a look around SourceForge.net as there is quite a lot of useful free software there.
Hope you find it useful