Partner Trade is a special name used for a Trade between the two members of a couple. All the usual rules for Trade apply:

Because the two dancers in a couple are facing in the same direction and standing next to each other, they will need to "pass right shoulders" while making small semi-circles.

The dancer on the right will flip over to the left, making a very small semi-circle. The dancer on the left will make a slightly larger semi-circle, going around the dancer on the right.

Note that they end up as a couple again, just as they started, except that the whole couple is facing the opposite direction.