I would use this feature most in portrait but also in landscape mode.
Regarding Aron's comment that "Unfortunately PDF cannot do this", one of my performing partners uses a different music reader app that has both native files and supports PDFs. This app can scroll PDFs (note, otherwise Unrealbook is far superior...). It has a field to enter song length (similar to a transmogrify button) and sets scroll speed based on that and the number of pages in the score. If scrolling is activated for a song, his page turner will start and stop the scroll.
I would use this feature most in portrait but also in landscape mode.
Regarding Aron's comment that "Unfortunately PDF cannot do this", one of my performing partners uses a different music reader app that has both native files and supports PDFs. This app can scroll PDFs (note, otherwise Unrealbook is far superior...). It has a field to enter song length (similar to a transmogrify button) and sets scroll speed based on that and the number of pages in the score. If scrolling is activated for a song, his page turner will start and stop the scroll.