WRKCO INC. as Issuer and WESTROCK MWV, LLC WESTROCK RKT, LLC and WESTROCK COMPANY. as Guarantors THIRD SUPPLEMENTAL INDENTURE DATED AS OF NOVEMBER 2, 2018 to INDENTURE DATED AS OF AUGUST 24, 2017 THE BANK OF NEW YORK MELLON TRUST COMPANY, N.A. as Trustee