Page numbers behave slightly differently, depending on whether you inserted them by using the Page Numbers command on the Insert menu or if you used the Insert Page Number button on the Headers and Footers toolbar.

Choose Header and Footer from the View menu.
Go to any header or footer (depending on where your page numbers are) and double-click on the page number to select it. If you used the Page Numbers command on the Insert menu, make sure you select the frame around the page number (it is similar to a graphic element).
Press the Delete or Backspace key to delete the page numbers throughout the document.   _{Your Comment}