If you want your page number in the footer, open the footer and press
Alt+Shift+P where you want the page number to be.
Alternatively, use Insert | Page Number, or use the Page Number button
on the contextual Header & Footer Tools | Design tab that is displayed
when you access the header or footer. If you don't want to overwrite an
existing header or footer, be sure to use Current Position.
More at
http://sbarnhill.mvps.org/WordFAQs/HeaderFooter.htm.