CUPS-PDF is available under the GPL and is packaged for many different distributions or can be built directly out of the source files. This software is designed to produce PDF files in a heterogeneous network by providing a PDF printer on the central fileserver. CUPS-PDF requires root privileges since it has to modify file ownerships. In order to ensure CUPS-PDF is running with the required root privileges you have to make 'root' the owner of the cups-pdf backend and set the file permissions...