[Zeke]

The only thing you need to know about hanging a pair of doors in one opening is hang one door, usually the inactive door, and then treat that door as a jamb while fitting and fussing with the 2nd door. Just leave it closed and take your measurements or scribe your lines like the other door is not a door.

Of course you have to get the first door in well enough to work properly. It's one, then two. Or rather one then another. if you think of them as a pair too soon, you will mess up.