How to spread a wide page of PDF on two pages area in flipbook?

I'd like to have the A3 wide page in my PDF so that I can have a big picture and text that spreads across both pages. And then how can I have the page go back to normal two A4 pages side by side again in converted flipbook?

The "Detect wide page" feature is for those PDF files which contains landscape pages to show on two pages area, for example, if the page 2 in your PDF is a landscape page which spread like two normal pages, the "Detect wide page" feature will help to show this page on two pages area as page 2 and 3 in flipbook.

The below screenshot shows you the details about using this feature:

The operations are easy too:

1. Start the program Flip PDF or Flip PDF Professional, import PDF with checking "Detect wide page" option;
2. Customize template, set background, toolbar, buttons, icons, etc.;
3. Click "Convert To Flipping Book", choose output format and then output in defined folder.