Created attachment 124208 [details]
demo

SUMMARY
I propose adding alternative scrolling behavior. It helps keeping up the reading speed in auto-scroll mode and it tires eyes less compared to traditional scrolling behavior. It's easier to show it once rather than explain it, so please check attached gif.

OBSERVED RESULT
In traditional scrolling entire page content moves upwards or downwards in order to make space for new or previous content.

EXPECTED RESULT
Keep page content steady. Have a separation horizontal line moving from top to bottom of a viewport. Everything below the line is a content of a current page. Everything above the line is a content of a next page. Line can be stylized as a shadow. Page is not necessarily a next page in a document but rather a viewport range of a document. 

ADDITIONAL INFORMATION
I would really love to have this feature in Okular as due to my work I have to read a lot of material every day, and this scrolling mode helps me reading faster. I've done a prototype, and it works for me, but as I'm not a professional C++/Qt developer the code quality is poor. Also I don't have enough time recently to continue working on it. There are some improvement I'd like to add to my current prototype (apart from using proper C++ and performance optimizations), such as: create visual controls for scrolling speed in auto-scroll mode, preserve original scrolling behavior and make on/off switch for new behavior in View menu.

By submitting this feature request I hope that it will help seeing the resonance  and feedbacks from other users, and, if not being assigned for implementation to some experienced okular developer, than at least helping me find somebody who would be able to cooperate with me on implementing this.