Advice needed for document createion (PDF-postscript?)

Hello all. I need to create a document template, were I can call it and sort of 'fill in the blanks'. What I'm doing is created a PHP based network fax system. I want to create a template for the fax cover sheet, and just fill in the needed info when each cover sheet is created. The template would consist of the basics: company logo, To:, From: etc, flields. The fax backend is based on eFax, which relies on ghost script. That leaves the possibility of creating PDF, postscript, or GIF as my out put. I know I could just create the entire cover sheet with the PDFlib, but I would rather just gernerate the info that changes from one fax to the next. Any thoughts on the best approach? Thanks, Chris PS: The fax system I'm working on allows for faxing from ALL MS windows applications that can print, and should be quite easy to provide the same for *nix apps. The source will be made available if anyone is interested.