If you look under Insert|Shapes, you'll see a wide range of circles, etc. that can be inserted into a document. If you insert an Oval, this can be resized/shaped as necessary. You can also use the Drawing Tools that appear when it is selected to change its fill (e.g. to transparent) and outline colour (e.g. to red). The outline thickness can also be changed.

Perhaps better still, the available shapes include callouts, which allow you to insert a box that can be typed in with a line pointing to the area under discussion. You can drag the callout lines around independently of the callout positioning.

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]