A certified copy is a copy (often a photocopy) of an original document (ie. your parchment). The copy includes an endorsement that it is a true copy of the original document by affixing a signature, seal and statement to that effect on the copy. It does not certify that the original document is genuine, only that it is a true copy of the original document.
Certified copies can be endorsed (signed) by a notary public, lawyer, or commissioner of oaths. The Registrar’s Office can provide a certified copy of your Dalhousie parchment. Your original parchment is required to make the copy which is endorsed by a Dalhousie representative with signing authority.