PDF Annotator does its best to display clear, sharp, meaningful, and sufficiently sized toolbar icons on all kinds of different screen resolutions, including modern high-resolution (high DPI) screens.
If you feel like the default size of the toolbar icons in PDF Annotator is too small, you can switch to Large Icons instead. Large Icons are 50% larger than the default Small Icons.
Start PDF Annotator and select View, Toolbars, Icon Size and either choose Small or Large.
As you see, after choosing Large Icons, all icons are now larger and consume more space on screen, but may also be easier to press.
The size of the buttons in Full Screen Mode does not depend on this setting, though.
Click here to learn how to set up the button size in full screen mode.