Exhibit 1.1 VAN KAMPEN UNIT TRUSTS, SERIES 791 TRUST AGREEMENT Dated: September 3, 2008 This Trust Agreement among Van Kampen Funds Inc., as Depositor, The Bank of New York Mellon, as Trustee, and Van Kampen Asset Management, as Supervisor, sets forth...Trust Agreement • September 3rd, 2008 • Van Kampen Unit Trusts Series 791
