Just FYI, might be worth keeping tabs on: http://gnupdf.org/
(GNUpdf)! From their website: "The goal of the GNU PDF project is to develop and provide a free, high-quality, complete and
portable set of libraries and programs to manage the PDF file format, and associated technologies." From what I've gathered, they just want a fully portable PDF library (unlike xpdf it's derivative poppler). They seem promising, and from what I've gather one of their goals is to be able to easily write different backends to it. Keep in mind they're still not even close to be done, though.