In book formatting, page numbers are strategically placed to avoid interference with the binding edge. They are alternately positioned on the outer corners of pages to ensure improved visibility and readability after the document is bound. When creating a PDF, the page numbers are situated on the right side for odd-numbered pages and on the left side for even-numbered pages.
The layout of your running headers/footers is controlled in your Theme under Print Settings> Header and Footer. Here you'll find a horizontal pane with all the options currently available, (you can scroll right to see more options).