I've managed to add a text-based watermark to an existing PDF using DDX and CFPDF. So far no problem.
If I open the new file I can see the watermark and all but if I try to print it inside coldfusion I can only get the page without the watermark. Even if I try to print the new pdf from Acrobat I get a "Document could not be printed" and the only way to have it printed is configuring the print settings as "Print As Image". In the DDX I've showWhenPrinting="true". This is supposed to be used on a automated batch process so, if anyone has any insight on this I would really REALLY appreciate it.