How To Insert Page Numbers on Master Pages in Adobe InDesign

InDesign will automatically number pages in the style you designate when the proper page numbering code is placed on the Master Pages of your document
Just Follow the bellow Steps:

1. Put Text Frame on Master Page.
   On a Master Page, place the type tool where you want the page number and draw a new text frame.
2. Add Preceding Text (if any).
   At the flashing insertion point type any text you want to precede the page number (or you can add it later). This might be a decorative dash or the word "page."
3. Insert Page Number Marker.
   Choose Layout > Insert Page Number (or Alt + Ctrl + N in Windows). A page number marker on a master page will display the master page prefix.
4. Format the Page Number.
   Format the paragraph and page number marker as necessary including adding additional text before or after the page number marker. You might surround the page number with decorative dashes or symbols, the word "page," the book title, or chapter and section headings.

 Notes:

1. Elements on the Master page are visible but not editable on all foreground pages. You'll see actual page numbers on the foreground pages.
2. To create different numbering schemes for sections of your document you would use the Section Marker command.