From “peter000″ on discussions.apple.com :
The ©, ® and ™ symbols are available in the Emoji keyboard, which can be enabled in Settings->general->Keyboard->Keyboards->Add New Keyboard.
These symbols will show up for anyone, even if they are not on an iOS device, they’re ascii symbols and not pictures like the rest of the emojis.
Tip: if you use these symbols lots, add the emoji keyboard, open up any text editor and type in those symbols. They’ll now be in the “recently used” section of the emoji keyboard for faster access.