How to make the overall size of flipbook smaller?

How could I make the overall size of flipbook smaller?

Changing width and height of flipbook is the best method to make the overall size smaller.

1. On the left option box "Design Setting", select "Book-->Page Width/Height";
2. Customize your own size for the output flipbook;
3. Don't forget to click button "Apply Change" to apply to the out;
4. Preview its effects.