That in part is what a scroll bar is. The one on the side of my firefox window right now shows i am about 1/4 down the page while writing this. I never understood this drive towards removing scroll bars from tablets. On phones they may eat up too much space, but on tablets? And now Apple appears to have stripped them out of OSX as well, so we can be damn sure that Gnome, Unity and Windows will follow suit.
Still, the latest ribbon idea from Microsoft seems to be to hide by default. With that, and perhaps setting a Word to fit the whole page on screen (much like a ebook or PDF) one could then use whole screen swipes to go back and forth (with some for paging interfaces that could come into view). Sometimes i wonder why they got the whole "ream of paper" idea from (tho the office toilet may be a good guess).
Still, i think MS is doing it this way to make the transition as painless as possible in terms of relearning. This is something they seem to always consider. Win8 may be the first time since Win95 that MS tries to do a whole new UI, and even with Win95 one could revert back to the Win3.x "desktop" if one wanted (it was hiding in the wings, iirc).