[palosanto]

Frank, 
Use the pan tool and drag the page down.

Even better: Use the arrow button next to the "closing-X" in the left top corner.

(Seems obvious in hindsight but I struggled for a while with the toolbar in the way as well until I found that)

Not sure about 'better' in this case. It means that you'll have to pick the text tool, pen tool or whatever you want to annotate with first, collapse the toolbar, do the annotation and extend back the toolbar once you are done.
But it's certainly an option