Because OXPS format is very rarely supported in programs and can be opened only using the default XPS Viewer in Windows 8 and later, many users would like to convert it to the previously used XPS format, because that format had at least a bit better support in 3rd party programs.
The easiest way how to achieve oxps to xps conversion would be Microsoft's command-line program called XpsConverter which works even in Windows 7. The syntax to convert oxps to xps would be the following:
XpsConverter /XPS /InputFile=sample.oxps /OutputFile=sample.xpsOpen OXPS file Open XPS file
A simple OXPS to XPS online converter
A XPS/OPXS command-line converter