The files are created by Microsoft XPS Document Writer, but can be opened by Microsoft XPS Viewer. You may access the Viewer directly, or open it through the file.

PDF2Office converts PDF and XPS files into editable Word, Excel, PowerPoint, OmniGraffle and other common file types by recreating the intended construction and layout of the document. Version 6.0 ...

The Microsoft XPS Document Writer saves your archived documents, Web pages and shared content as XPS files. Windows 8 includes an XPS Viewer that opens these files in a readable format.