Section 20. A certificate issued by any society shall specify the amount of death benefit provided by it. The certificate, the charter of the articles of organization, or, if it is a voluntary association, the articles of association, the constitution and by-laws of the society, the application for membership, the medical examination, if any, signed by the applicant, and all amendments to each thereof, shall constitute the agreement between the society and the members. Copies of such documents, certified by the secretary of the society or corresponding officer, shall be received as evidence of the terms and conditions thereof. Any changes, additions or amendments to the charter, articles of incorporation, or articles of association, constitution or by-laws duly made or enacted subsequent to the issuance of a benefit certificate shall bind the member and his beneficiaries, and shall govern and control the agreement in all respects in the same manner as if such changes, additions or amendments had been made prior to and were in force at the time of the application for membership. The language in the preceding sentence shall be incorporated in substance in every benefit certificate hereafter issued.