Want to develop your PDF Viewer, Use Poppler

Poppler is a open source C++ library to render PDF. Its QT4 interface helps you develop application for linux, windows and Mac OS/X. The library has been used extensively by open source GNOME or KDE environments.

I used the library sometimes back. You can build demo application without any hassles using mingw compiler. 

QT also runs a nice tutorial on how to use Poppler library. On Windows you may also need libfreetype-6.dll  alongwith poppler DLLs (libpoppler-13.dll, libpoppler-qt4-3.dll) required to render freetype fonts.

Poppler is based on another popular pdf rendering library XPdf. When you build the library, it also build useful tools like pdfinfo.exe, pdftotext.exe, pdftohtml.exe.

The only limitation is that it may not play flash video embedded in Adobe's propriety PDF.