I make PDF files all the time. Why do I need XPS? Or do I?
i don't think you need it if you're asking this question. PDFs work everywhere!
What is the XPS Viewer?
An XPS document is any file that is saved to the XML Paper Specification or .xps file format. Although you can create XPS documents (.xps files) by using any program that you can print from in Windows, you can view XPS documents only by using the XPS Viewer.