I am preparing a line-by-line translation of a Latin text (i.e. line
1-latin; line 2-trans of 1; line 3-latin; line 4-trans of 3 etc.).

I also want to be able to 'comment' certain words in the Latin (maybe a
bubble in the margin? - like Word's 'comment' feature).

And if possible it'd be good to edit all the English one time, and all
the Latin another.

Does anyone have any ideas about software (Mac OS X)
which would be good for this?

Thanks for your help.