Ability to completely turn off collapsed sidebars
Please for goodness' sake give users the option to completely remove the left and right sidebars instead of merely collapsing them. For users using Reader, the vast majority of the time all they will want to do is only read a PDF, and many will want as much screen space as possible to do so.
For the average Reader user, in the left toolbar the only thing they may want is thumbnail or chapter view. This could be on the top toolbar, with the other options available on a drop down menu from that button if you really must keep them there. The right toolbar, meanwhile, is completely redundant with the "Tools" pane. Being made up of options for creating and editing, these merely get in the way for Reader users who just want to read. The collapsed bar can easily be clicked mistakenly when attempting to scroll, and when a PDF hides the scrollbar (which there doesn't seem to be an easy way to either disable or re-enable), the collapsed bar will likely be mistaken for the scrollbar period.
I understand that these are considered 'features', but for many users they are merely an inconvenience. In many, many other programs, side toolbars are dockable and can be moved or closed. There are so many other options on how it could've been implemented that aren't so aggravating. Please either use one, or give users the option to completely disable them.
The collapsed Right Tool Pane violates usability principles. To quickly scroll a page, users can no longer just drag the mouse cursor all the way left, and click on the Right scroll bar. This would probably take only 1 sec. With the annoying Right Tool Pane collapsed, users must now carefully drag the mouse cursor, take aim so-as-to not click on the Right collapsed pane, then can he/ she click on the right scroll bar. This is really inefficient.