How do I add page numbers to my document?

InDesign allows you to add a text box to mark where page numbers should go and then automatically edits the box to match the page number as specified in the pages palette.
This should be done in the master, so go to your master and make a new text box. Place the text box on your page in the place where you want your page numbers to appear. Type any text you want to have appear before the number (so if you wanted it to say Page 1 rather than just 1, type Page into your text box.
Now go to Type, Insert Special Character, and Current Page Number. Don’t be confused when a letter appears in the box instead of a number, its just the prefix of your master. If you double-click on any of your pages to which you have applied your master, you should see the correct page numbers appear in the text box.
Make sure that you put page numbers on both pages, if you are working in a two page master.