You can buy it directly
here. It works as a plugin for Acrobat, Quark, and InDesign. You can start in Quark or InDesign and designate what text or graphic boxes contain variables, then you export to PDF and insert your data fields, then once everything is good you compose the document into its final format (it can do several formats, including PDF, PPML, JLT).
You can also skip the Quark/InDesign step and add variables to any PDF, but if position is critical it is easier to start in the layout app.
