Saving XDP form in PDF format at the end of the process

Hi,

I want to save my XDP form to a file system as PDF documents at the end of the workflow. There is a service writeDocument to writing PDF files, which accepts 2 parameters as input

pathname -- type : string
document -- type : document

In my workflow , I have an Xfaform variable which holds my form data.
But, as service requires the parameter as document I could not pass this variable to service. I tried to define a process variable of type document
and assign my xfaform variable to it, then pass this variable to the service. A pdf file is generated but not valid (1 k).

My question is how should I pass the variable to this service?

Thanks in advance

Regards

Cihan