generating .PDF

Hey guys, just wondering if anyone has any experience of generating PDF files from webpages ? I need to basically fill in a pre-existing PDF table using webpage form data. Perhaps with a way to save some kind of intermediate file (XML maybe?) so they can make small changes and have it re-rendered (or come back a few days later, make a few changes and upload the new XML file for a re-render..)

PDFlib looks really nice. Trouble is, I don’t think the free version can open existing files for editing, so I’d have to render the entire form everytime, instead of just filling in the text spaces. Anybody got any cool ideas or should I just do it this way?

Cheers, James.
pembsdoe.org.uk