Follow some steps...
Step 1: Open Microsoft Word Application.
Step 2: Go to the top of the window application at the ribbon and click the "Insert" button.
Step 3: Go to the "Header & Footer" group and click the "Page Number" button as shown in below picture.
Step 4: After you click the button "Page Number" there will be shown another sub-menu with some buttons as shown in picture below.
First button is "Top of Page". This button let you insert a page numbers at a top of page. There are different positions to insert a page numbers, at top left, top center, top right and like a bar with text at top of page, see picture of these options.
Third button is "Page Margins". This button let you insert page numbers at margins place. See the picture of these options.
Fourth button is "Current Position". This button let you insert a page numbers at the position that you have put the cursor (pointer) and have different positions of page numbers. See the picture above with default options.
These are the options for inserting a page numbers on document pages at Microsoft Word Application.
For other information's like formatting page numbers read other post...