Scribus is really great. It does take some getting used to (like if you want auto page numbers, you have to set it on the master page), but it does a fantastic job.
The fun thing about PDF files is that they are universally compatible.
If you have another program you want to use but that can't make PDF files, you might want to check out PDF creator forge. It's a special printer driver that will turn anything into a PDF. If you install it, just make sure you do a custom install and don't install the architect component. It's a commercial and a bit of a piece of junk.