Another couple of suggestions, in this case regarding the annotation bar:
I think that it would be nice if the buttons "Add annotation" and "Erase annotation" were toggle buttons, this is, with one clic you enable the mode and with another one you disable it. I annotate a lot, but I also like to turn the page using the touch screen, so now I have to change the toolbar to "General Toolbar" everytime I want to stop annotating.
My other suggestion is regarding the "Hand tool". Is there a way to reset the screen to its previous state after using it? If not, it would be nice having this option. I've used the hand tool by mistake and I've spent a lot of time trying to visualize the book correctly again.