I discovered a neat little trick...not a cheat...maybe it's already known but it wasn't to me.

How do you get Daedric Arrows?

Race to the closing of this topic begins

Reverse pickpocket archer NPCs or give them to a follower?

First you have to have some...I had four in my inventory.

Then, you need a follower that uses a bow.

Take all arrows from your follower.

Give them one of your daedric arrows.

Your follower will use nothing but daedric arrows as long as all they have is the one in their inventory. The one becomes an infinite supply for them.

Every time you get into a fight, draw your bow first and begin shooting at a far enough distance that your follower will follow suit--shoot arrows, IOW.

Check the bodies.

I just discovered this a couple of hours ago and I now have ten and Lydia still has her 1+