Check out the other tools on the Drawing tab. Use the Panning Hand tool to move to hidden areas on the right or at the bottom of a page quickly without page down or arrow keys. The Lasso Select tool lets you literally draw a lasso around a selection with ink strokes, shapes, etc. and delete them, change their color, or resize them. Explore the whole color palette for your pen and highlighter tool by clicking on the down-facing More button and choosing More Color & Thickness Options.
These tools can really unleash your creativity on a touchscreen device!