If you are financing through Disney you need to go in front of a notary for the short form mortgage paper. We just added 100 points and need to do the same thing.
I'm not sure if add-ons are different than purchases.
We purchased last month (also at BLT). We received the FedEx package. In our package, one page had to be signed in front of a notary and notarized. The rest did not.
In the packet of papers you will see a telephone number for the Quality Assurance (QA) team from DVC. They can answer all of your questions regarding your purchase contract, including whether any signatures have to be notarized.