Here is how to do it:
1) Open PDF XChange Viewer
2) View -> Toolbars -> Customize Toolbars...
3) Click on 'Commands' tab
4) Under categories select 'View'
5) Scroll down to 'Pages Navigation Toolbar' and click it
6) Click on the 'Properties' button below
7) Under Shortcut Click on 'Keys' textbox
9) Click Ok, Click Close
10) Enter full screen mode (F12), press your shortcut keys... it appears on the bottom.
Useful for when you are viewing a pdf in full screen mode but there are no page numbers in the document. Enjoy!