1. Enter reading page -> Page Display; 

2. Then you select Vertical or Horizontal from Scroll Mode to scroll pages vertically or horizontally;

3. And you can choose to view pages with Single Page or Two Page from Display Mode, tick Continuous Scroll and you can scroll and view pages continuously, click Read Mode and you can read the documents in full-screen mode.

Or you can right click anywhere in the PDF and choose Vertical or Horizontal, Single Page or Two Page, tick Continuous Scroll and click Read Mode On or Off from the pop-up menu.