I just spent the last few hours trying to find a simple editor for PDF files that will let me type text on top of a scanned file. I tried everything. For some reason I cant even seem to find a trial version of Adobe Acrobat online. I didn’t want to pay $60 for such a simple thing. Then I came across a small application called formulatepro hosted on google here http://code.google.com/p/formulatepro/
This is a super simple app that allows you to type pdf’s as well as draw simple shapes. You can adjust the font and color, all the basic text tools that apple includes in its text editor. The basics but its exactly what I needed and free!