How to Use a Page Break in Designer
Page breaks are really useful when you want to split or move content from one page to another.
You do that by going to the 'Elements' section. Grabbing the page break element and dragging it into the content. It will then split and push the content below the page and move it onto the next page.
It's marked by the highlighted area in the footer. This means that any re-pagination that goes on within a document, will respect that page as it is and will not compact the content.
If you delete the page break...
... and then re-paginate, you'll see it pulls the content up again.
That's how you use page breaks in Designer.