Choose Insert > Page Number.
Choose a location, such as Top of Page or Bottom of Page, and then pick a style in the gallery. Word automatically numbers every page.
Tip: Want to change the appearance of the page number you just added to your Word document? On the Home tab, choose Font, and change, for example, the font style and family, and font size and color.
When you’re done, choose Close Header and Footer, or double-click anywhere outside the header and footer area.
Tip: Word automatically numbers every page, but you can change that if you want to. For example, if you don't want the page number to appear on the first page of your document, double-click or double-tap near the top or bottom of a page to open the Header & Footer Tools Design tab, and select Different First Page. For more options, choose Insert > Page Number > Format Page Numbers.