To delete a section divider, flip to the divider page using the navigation bar and click the red trash can button next to the page.
To delete multiple pages, click on the Arrange Pages button. There are two ways to select multiple page depending on how the pages are situated. If all of the pages are consecutive, then you can click on the first page, hold down the SHIFT key, and then select the last page to highlight them. To select pages that are not consecutive, you will click on each page individually while holding down the Control key.
Once the pages you want to delete are highlighted, click on the Delete Pages button in the top right hand corner.