When reading long wall-of-text documents with overlap (often caused by zoom-page-width), it can be very hard to keep track of one's reading position when paging down. This would be easily fixed by optionally dimming the overlap (already read) portion of the screen. Alternately, just putting a line across the screen at the overlap would be a huge help.
What... overlap? Did you turn that on at some place? (Where?) I came here with the feature request to have (some, ideally configurable) overlap when using PgUp/PgDn in Continuous Mode. In the PDF document I'm currently reading, Okular will skip by _exactly_ the whole page, even when that means splitting a line of text in half. ...
When I made this request 9 years ago, it was at the bottom of the "General" settings tab. I'm not presently using KDE so I don't know.