How to adjust the length of your page
The height of a page is primarily based on the content on the page. You won't be able to set the height of your page above where an object is placed on that page, so there may be times where you need to delete or resize an item if you want to make the page shorter.
Using the handles found on the dotted line at the bottom of your page, click and drag the page height up and down to increase or decrease the length of the page. Like the video above mentions, you may need to look around the page using the Select All tool for items that are preventing you from reducing the page height.