PDF < FDF < $_POST

I need PHP fill out the form fields and prepare for download a PDF from an HTML form submission. One way would be to use a PDF with pre-configured form fields where an FDF is created from PHP. The FDF 'merges' with the PDF when the FDF is opened. I got all that from: <http://koivi.com/fill-pdf-form-fields/>. I have the scripts from koivi.com producing the FDF correctly but I don't know what to do with it next. The target PDF would need to be downloaded first because when you open the FDF is says, "hey where's the target." fdf_open looked promising but the fdftk is not compiled in on the server. Thanks