The PoDoFo library is a free, portable C++ library which includes classes to
 parse PDF files and modify their contents into memory. The changes can be
 written back to disk easily. The parser can also be used to extract
 information from a PDF file (for example the parser could be used in a PDF
 viewer). Besides parsing PoDoFo includes also very simple classes to create
 your own PDF files. All classes are documented so it is easy to start writing
 your own application using PoDoFo.