Convert XML doc to PDF

Hello everyone,
I tried for days to find out an answer to this but couldn't solve it.
I created a program for generating XML files for invoice of a given document number.
I managed to save that xml file to local pc. But also I need to convert that XML file to PDF ( from my program) and I got stuck here. Can anyone help me out?

Here is my code.

IN BETWEEN HERE I AM CREATING NODES FOR XML