As a standalone app, the @PrintByXerox app currently does not support PIN or shortened ID authentication. At this time, entering the Email address is only valid authentication method.
However, I would like to share that if you are a Xerox Workplace Suite (XWS) or Xerox Workplace Cloud (XWC) user, the @PrintByXerox app is part of that offering. Using either XWS or XWC with the app would allow you to authenticate at the device using your corporate badge, your phone or an alternate login ID.
I hope that this information is helpful, but please let me know if you have any additional questions.