Important: A different page formatting can be applied to each chapter of a document.
To recapitulate – page formatting includes:
▪Page size, orientation and margins
▪Headers, footers and master pages
▪Page numbers (initial value, format)
When you start a new document, it consists initially of a single chapter. If you change the page formatting, it affects the whole document.
If you now divide the document into several chapters with the command Insert | Break 
| Chapter break, the new chapters initially assume the page formatting of the original document. This is because the following applies:
Important: When you insert a chapter break, the resulting new chapter initially assumes the page formatting and the master page of the current chapter. However, you can then change the page formatting and master page separately in each chapter.
For each chapter, for example, you can now create different headers and footers or set a different paper size, etc.