If I get the Rings of Mara from the Imperial Edition, does the friend I decide to perform the ceremony with also need to have purchased the Imperial Edition in order for us both to get the bonus?
Only one copy of the Imperial Edition is required. When you purchase the Imperial Edition, you receive the Pledge of Mara. This is the item you use to get the Rings of Mara. Only one Pledge of Mara is required—both people do not need to have it.
The pledge can be equipped for use. Two characters can approach a Shrine of Mara within the game. While standing on sacred ground, the character with the pledge can target the character without and then use the pledge to evoke the Ritual of Mara. Both characters must agree to share this commitment. Upon acceptance, a celebration occurs and the rings are placed in each character’s inventory. The rings are marked with the name of the matching character. While wearing the ring and adventuring with the corresponding partner, both characters will receive a bonus to their experience. This bonus stacks with others.
Each pledge can only be used once. The names on the rings cannot be changed. This union is forever.
http://elderscrollsonline.com/en/news/post/2014/02/18/ask-us-anything-variety-pack-13