Page numbering is indirectly an attribute of page styles. Consequently, you need at least two page styles for your book: one for the first 5 pages, one for the chapters. Unless your first 5 pages are not numbered (usually i, ii, iii, …), you’ll also need a separate page style for the cover without page number.
Once you have defined the needed page styles (or used some built-in ones), enable the header or footer where you want to insert page numbers. In the header or footer,
You must now force page numbering to start at 1 on the first page of the first chapter.
At the end of the first part of your book (after the last paragraph of the first 5 pages),
Manual break (don’t use
Page break because it does not grant you access to break attributes). Select the chapter page Style from the drop-down menu and force page numbering to restart from 1.
Follow @gabix’s advice and read the manual or, at least, the built-in help.
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