Notarization is meaningless. What really makes sense is how to make the other party accept that you can use an alias instead of your real name, so as to avoid falling into doubts such as "fraud" when you can't perform the contract. So it can be clearly defined through the contract. After all, when the other party examines the official document you signed, your real name does not match your pen name. You definitely need to explain this. In this case, as long as you show that the document signed by a pseudonym is equally binding on you, then there is no problem.