As you learned in Chapter 19, WPF supports two complementary types of documents. Flow documents handle flexible content that flows to fit any page size you specify. XPS documents store print-ready content that's based on a fixed-page size. The content is frozen in place and preserved in its precise, original form.
As you'd expect, printing an XpsDocument is easy. The XpsDocument class exposes a DocumentPaginator, just like the FlowDocument. However, the DocumentPaginator of an XpsDocument has little to do, because the content is already laid out in fixed, unchanging pages.
Here's the code you might use to load an XPS file into memory, show it in a Document-Viewer, and then send it to the printer:
// Display the document. ...