Please install the PdfHandler extension on Wikimedia servers.
The handler suports Pdf files, extracts pages, generates thumbs from extracted pages and displays Pdf files in multipage view like DjVu. It works together with ProofreadPage and embedding images with [[Image:Bla.pdf|page=5]] works too. The extension was tested by Raymond and me. A preview works under http://www.xarax.eu/wiki/Bild:110.pdf. The extension would be usefull for proofreading on all wikisource projects, but also to make image thumbs on all wikimedia projects.