The tool switch is a button that always hovers in the bottom right corner on top of your document, which enables you to switch your current tool with a single click.
By default, the tool switch shows the Pan tool icon. Click once on the tool switch, and you're in Pan mode. Now you can use the mouse, stylus, or your finger to pan the document.
If you prefer to use the Tool Switch to switch to another tool than the default Pan tool, you can set a different Target tool under Extras Settings Display Tool Switch.
After having switched to Pan mode by clicking the tool switch once, the tool switch now displays the tool you worked with before you switched to Pan. Another single tap on the tool switch will take you back to that tool. So, it's one click to Pan mode, one click back to your previous tool.
A right click (or long tap) onto the tool switch opens a menu that includes a list of all tools you worked with most recently. Using this menu, you can quickly switch between a number of tools you worked with recently. The same menu pops up when you click or tap on the tool preview in the top right of the document window.
You can move the tool switch to another position above your document if it's in your way. Just click the tool switch, hold the button down, and move. Or tap, hold, and move if you work on a touch screen.
If you do not want to use the tool switch at all, you can disable it. Click Extras Settings Display Tool Switch and uncheck the Show in regular mode option, if you don't want the tool switch to appear when you run PDF Annotator in a regular window, or Show in full screen mode, if you want to remove it from Full Screen Mode only, or both. Even if you disabled the tool switch, the Most Recently Used Tools menu will still be available by clicking the current tool preview in regular mode, as described above.