Can the Portal be edited on Ghost Pro?

I would like to add some additional copy before the sign-up boxes/tiers and probably a different logo/image. I couldn’t find any relevant file in my theme.

Yes it can be . You can add text links, whatever you want.

It is done directly in the portal, no need to go into your theme. Done from admin dashboard.

I can only see Portal Settings and the Tiers, which I know I can edit. I want to add some persuasive copy before the Email and Name boxes.