All participants can access their tickets using their edit codes displayed on their receipt or by going to their profile.
There are 2 types of edit codes.
Order edit-code: Can makes changes to all participants on that order including changing owner (if activated).
Participant edit-code: Can make simple changes to the participants sign up. Cannot change owner.
You decide how much the participants are allowed to change with their edit-codes.
Go to Participants and Changes and check the boxes they are allowed to change.