I’ve been using LyX (a What You Get Is What You Mean document processing system) to prepare various documents for a couple of years now. Since moving to the Mac I’ve had trouble with any PDFs I create using PS2PDF from LyX, all the text in the PDF became rendered vectors, rather than selectable text. Effectively the whole document becomes pages of high resolution images, rather than text.
As well as making for file sizes in the tens of megabytes from a few hundred k of ASCII, it also means the PDFs are uneditable – this makes collaboration on a document rather hard…
The solution, obvious now I think of it, is to make sure in LyX that the document fonts are set to one of the 14 base fonts supported by the Adobe PDF standard (Times or Times New Roman, Helvetica or Arial, Courier, Symbol and Zapf Dingbats; this adds up to 14 when you consider the bold, italic, etc version of these fonts).
If you are also having this problem in LyX go to Layout:Document:Fonts and select something other than Default. You should now be able to edit your PDFs.