Manipulating PDF

Hi, I know it is possible to create PDF's and read them within PHP. But I'm after a method to read a PDF file, analyze it (dump structure or whatever) and being able to modify it in a valid way. And with modifying I don't mean just replacing text. I want to be able to remap layout, change fonts, change standards (if possible, I don't know). In other words, I want to have full control on the PDF and output it to my definitions. At least I want to be able to analyze PDF's so maybe I can built things myself upon the format. Has anyone seen such a thing for PHP? Or does anybody has a hint how to start doing it myself (maybe examples in Python or C which can be ported)? Again, I'm not after PHPLib or FPDF, since these libraries are either old or insufficient for what I want. Thanks in advance. Aschwin Wesselius