You can either add a UserID field to the photographer document type or a PhotographerID to the UserSettings System Table in the System Tables development section.

Look at Kentico alternative forms for some forms to edit their profile.

If this is something where you won't have a huge number of registrants, then you can manually create the photographer document when a photographer registers and set the ID on the User account manually.

Otherwise, you may need to get a little deeper into the code and create a custom registration web part that will create the photographer document and associate it with the user when they register. It might actually be easier to add that code to the login control because it is a much simpler control to edit. In your code you can check if a user has a photographer associated with him when he authenticates, and create one if not.



Alternatively, you can forgo the photographer document type and just add the fields that you had planned to add to it to the UserSettings table. Then use the user contributions web parts to allow them to add photos and things.

I hope this is enough info to steer you in the right direction.