It's not particularly clear. The instructions say University degrees do require original transcripts in sealed University envelopes, but I have heard of notarized degree certificates being accepted. As well as the original transcripts we are making copies of our degree certificates and getting those notarized.
We're trying to get as close to the "letter of the law" as possible since we want to give the Visa office as little reason to fail our application as possible!
Copy of all the educational documents, sealed transcripts from educational institute.
You must send degree or diplomas along with transcripts of the Principal Applicant and Spouse.
These Education documents must be notarized.