In your report you can have multiple different layouts and parts of your document. The page layout specifies page size, margins and content of headers and footers. Each part of the report, called a Page Set, uses one or more page layouts. It is in the page set that you define the content of the report. For example you can have a cover page with one layout and no header/footer and one page set with the RDS for each room that has another page layout. You can even have different layouts for different header/footer for odd and even pages. For example:

In order to view the pagination setup, make sure to check the pagination check box in View → Show/hide → Pagination.

Page Layout

To add a page layout, right click on the "Layouts" and select "Add page layout". To rename a page layout, right click on the layout and select "Rename".
A document layout has the following regions:

You can edit the page layout by either double clicking on it in the pagination window or selecting an option from the menu: Page Layout →Layouts

In the page layout properties window, you can define both the page size in general (in the Page properties) and the size of the different regions.

Important: The body region (where the main content of the report is added) does not have a size (the page has it), but it has margins and padding. The margin is the total margin from the page size to the body content. So if you for example would like to have a header that is 3 cm high (Extent) you need to set both the extent of the header and make sure that the body has a top margin of at least 3 cm. Otherwise, the content of the body and header would overlap. If you check the precedence option for the header or footer it will fill the total width (precedence over the left and right regions):