You can simply print OXPS documents to PDF format using the virtual PDF printer in Microsoft Windows 8 or later if you have one installed on your computer, which is usually installed on modern system in the form of Microsoft Print to PDF printer. You can achieve oxps to pdf conversion simply by opening your .oxps file in the default Windows XPS Viewer and using the File ► Print function (select virtual PDF printer) to get your .oxps file as .pdf file.
If you are still on Windows XP or even older, you will have to rely on some 3rd party conversion options, but the chances that some of them support OXPS format are somewhat slim.Open OXPS file Open PDF file
One of the many XPS and OXPS converters
One of the many document converters for Mac
An XPS/OXPS to PDF conversion services
An XPS/OXPS reader for Mac