I know I can change the page size for my lesson in the lesson settings window, but the height seems to be fixed for the entire lesson. Is there a way I can make some pages taller than others?

Hi Pat,
There is!  Make sure you are on the latest version of SmartBuilder (Help > About SmartBuilder ... should be version 4.3.1).  If so, then you can go to Edit > Lesson Settings, and uncheck the value that says "Use the same height for all pages" and press OK.

Now on each page you'll notice a ruler along the left edge, and at the bottom of the page is a gold guideline with an arrow.  You can drag that arrow up and down to alter the size of that particular page.

Here's a video that shows the process in action - https://www.screencast.com/t/rs87mgAkcn6

Hope that helps!