In response to your request in FSF newsletter I have prepared a list for you. I have not used these but it is worth looking at for your list of Free software PDF viewers
TXTreader4linux http://code.google.com/p/txtreader4linux/
PDF Mod is for manipulating PDF files obviously first it opens the PDF for viewing so if might be useful for your list of Free software PDF readers https://live.gnome.org/PdfMod
eBook speaker Linux software for the visual impaired and more open source but what exact license? http://web.inter.nl.net/users/lemmensj/
ViewPDF -> Vindaloo +PDFKit -> Popplerkit http://home.gna.org/gsimageapps/
Hope this helps Best wishes Shahram
P.S. I have sent this message before from another email. Please delete that email. If you need to get in touch use my fsfe email.