I don't know of any way that you could do this directly in Protege.
You could do this in WebProtege, however, with the bulk operation "Set annotation value...", which is
accessible through the context menu in the Class hierarchy view. You
can select multiple entities to assign all of them the same
Another option would be to manipulate the ontology outside of
Protege, or use the Cellfie plug-in  (Tools
-> Create axioms from Excel workbook...) to
import annotations that are specified in a spreadsheet.