Where did you place the page numbers? On a master page where they should be? Look up Page Numbering in the help. It should help you to do it correctly.
If they are placed on the Master Page(s), and you can view them on the document page(s), then they may be on a non-printing layer or have been set to not print (Attributes panel).
Place them on the master on their own layer at the top of all other layers. Make a text frame, insert Type > Insert special character > Marker > Current page number