PDFlib is a library which allows you to generate files in Adobe's Portable Document Format (PDF). PDFlib acts as a backend to your own programs. While you (the programmer)are responsible for retrieving or maintaining the data to be processed, PDFlib takes over the task of generating the PDF code which graphically represents your data. While you must still format and arrange your text and graphical objects, PDFlib frees you from the internals and intricacies of PDF. PDFlib offers many useful functions for creating text, graphics, images and hypertext elements in PDF files.
The PDFlib home page has more information.