You can adjust the setting to lock vertical/horizontal rotation and auto rotation.
Lock Horizontal / Vertical
1. Tap "Tool" at the top bar. The menu page will pop up.
2. Tap “Lock Horizontal" to lock/unlock it.
△ Note: By locking horizontal scrolling, you will only be able to scroll the pages vertically.
1. Tap "Tool" at the top bar.
2. Tap "Lock Rotation" to lock/unlock it.