What is the best way to create PDF documents?

I have a client who sends out postcards to his clients.  Currently he is using a MS Word mail merge system, and he wants to switch to a more automated system using ColdFusion.  I have the original document as a PDF, and I'd like to use ColdFusion to populate the fields.  He also wants to be able to edit the non-filled information.

Is it easier/better, to use the original PDF and fill the form using cfpdf, or should I generate the entire document in ColdFusion (using cfdocument, maybe?) and then convert to a PDF?

Thanks!