Always screen on
- The "Screen always on" option must be provided because it's helpful to read in screen on mode without the interruption of screen off.
For anyone visiting here for this feature-
There are many similar requests like this, might help if votes are concentrated. For reference, following one seems to be well detailed: https://acrobat.uservoice.com/forums/595576-acrobat-reader-for-android/suggestions/44799325-always-on-display-when-the-app-is-open