Must a seal be an embossed seal?

No, a seal does not have to be an embossed seal. A seal can also be a wax seal or a rubber stamp seal. An embossed seal is a type of seal that is created by pressing a metal die into a piece of paper, leaving a raised impression. Wax seals are created by melting wax and then pressing a metal stamp into the wax. Rubber stamp seals are created by using a rubber stamp to transfer ink onto paper.