Microsoft Word for Mac page number

Press Opt+F9 (or Fn+Opt+F9) to toggle display of Field Codes

From my webpage: The Function Keys and Keyboard Shortcuts That Manipulate Fields

Shift+F9 is also a toggle shortcut, but it is a temporary one. Opt+F9 changes your system preferences. If the document is opening with { PAGE } displayed, you need the system preferences changed.