review of Notable PDF I mentioned it would be nice to easily create a circle or a box.
Looks like Notable PDF has added that functionality in this recent update. This will make it much easier to annotate image laden PDF's irregardless if you are using the touch screen or touch pad.
In the video that follows I go through all the tools since many have been added in the past year. Drawing Mode and Shape Mode really make Notable PDF the go to editor for Chrome OS.