Texpad's editor supports various gestures to aid your writing. These include,
Swiping two fingers left or right on the editor view will move the cursor left or right, swiping two fingers up or down will move the cursor up or down.
Select text and swipe three fingers right to comment out LaTeX source, and left to uncomment it again.
On the iPhone, Undo is currently available via the iOS's standard shake-to-undo gesture, raising the following dialogue
On the iPad however, the undo button is located on the numerical keyboard.