How to: Insert Page Numbers in Header or Footer

While editing the document’s header or footer, you can insert fields specifying the current page number or the total number of pages in a document.

Enter the header/footer editing mode. For this, double-click the existing header or footer, or use the Header or Footer command button to insert a new one.
To insert the number of the current page or the total number of pages in a document, use the Page Number and Page Count buttons on the Header & Footer toolbar or Ribbon page group.