Inserts the current page number as a field at the cursor position. The default setting is for it to use the Page Number character style.
Choose Insert - Field - Page Number
If you would like to define a different format or modify the page number, insert a field with Insert - Field - More Fields and make the desired settings in the Fields dialogue box. It is also possible to edit a field inserted with the Page Number command with Edit - Fields. To change page numbers, read the Page Numbers guide.