When you create your xfaForm variable you need to configure a render service (under Advanced Settings).
The render service is responsible to render the actual form (xdp) into a PDF. Usually you choose the renderPDFForm from the Process Management to render the pdf.
If you look at that renderPDFForm process, you'll see that it uses the variable /process_data/@formUrl to specify the url to the xdp. This variable is set when you configure formURL property of the render service (under Advanced Settings).
Usually we set it to Task->Form URL, but you could use your own variable there that contains the path to your XDP.
Another way is to just use a Set Value step to set the xfaForm variable's formUrl value to the URL of the form you want to use. Then you don't need to mess with the Render process parameters.<br />From memory, it would be something like:<br />/process_data/my_xfa_form/object/template_url = <URL of your template><br />Howard<br />http://www.avoka.com