Signatory (noun)

A person or organization that has signed a document, especially a treaty or agreement.

Origin:

From sign +‎ -atory, from latin signatorius, from signare ("to sign").

Examples:

1. The signatories of the peace treaty gathered to celebrate its signing.
2. The signatories of the agreement pledged to work together to achieve their common goals.
3. All of the signatories had to be present to sign the document.
4. The signatories of the treaty had to put their signature on the document.
5. The signatories had to agree to the terms and conditions of the agreement before they signed.