Yes, with use our wonderful flash flipbook software, you can total control the page size (width and height).
Here are steps in detail:
Step1: Download our flash flipbook (Boxoft PDF to Flipbook), and then install it in your computer;
Step2: Open Boxoft PDF to Flipbook, import PDF files for conversion
Step3: Find out Book Proportions under Design Setting panel (Design Setting -> Flash Display Settings -> Book Proportions)
Step4: Set book width and height on “Page Width” and “Page Height” bar.
At last, click “Apply change” button to refresh your flipbook, then you will find the book proportion has been changed.