The question you asked is actually not about FormsCentral. I think you want to convert an xps file to pdf. I'm not sure about how you get the xps file. Did you print the source file to xps? If it is possible, my suggestion would be that you try to convert the source file directly to pdf, without printing to xps.
You may go to the forums of Acrobat for more info: http://forums.adobe.com/community/acrobat