You can add page numbers to your document that automatically adjust as pages are added or deleted.
Tap 
, then tap Document Setup.
Tap the field where you want the page number to appear, then tap Page Numbers (you can use any combination of the fields for your header or footer).
Tap a page numbering style.
To change the number’s font, font size, color, or alignment, select the page number, then tap 
and make any adjustments.
Tap Done in the top-left corner of the screen.
You can set a starting number or change the number format for a page in a page layout document.
Tap the page numbers at the bottom of the screen to open page thumbnail view, then tap the page you want to change.
Tap to open Page Layout.
If the popover that opens doesn’t say Page Layout at the top, make sure you either selected the page in page thumbnail view or tapped an empty spot on the page (so nothing on the page is selected).
Tap Page Numbering, then tap “Start at” and decrease or increase the page number.
Choose an option below Numbering to change the numbering style.
If the next page in your document has Match Previous Page turned on, its page number increments to the next number and uses the numbering style of this page.