Bookmark Navigator - internal button shadow
Bookmark Navigator - deselect not immediately apparent
When you apply a deselect functionality and then deselect the button, visually it stays selected until/unless you move your mouse away from it and then back over it. This failure to visually refresh immediately will leave users confused (as it did me as the developer).
Page View - Add custom zoom option
Many times the three available page view options (Fit to page, Fit to width and Actual size) are insufficient. The user should have the ability to select their desired zoom level. This ability should exist in the desktop, mobile and services versions and should be saved from the last session.