You’ll be gathering several InDesign documents into one Book file to create a book. If you’re just getting started on your chapters, it’s best to design one of your more complex chapters first, then use that chapter as a template for all the remaining ones (i.e., “Save As” Chapter 1, delete all the original chapter’s text, place the Chapter 1 text, and thereby leave the trim size, margins, and styles intact and consistent among all chapters).
A best practice that we recommend to our clients is to create a base/folio master –with styled and positioned footers and current page number special characters– on which all other masters are based. This allows a footer that may contain date or issue information to be updated once and the changes are reflected in all of the master pages. If your masters only have current page number special characters then you can just add them to each master and the page numbers will be reflected when each master is applied to your document pages. document numbering in indesign