A system for associating documents with articles in a shipping container. The system includes an envelope having a generally flat body portion with an open end, first and second overlying flap portions extending from the open end and having oppositely facing exterior surfaces. The system also includes a shipping container having a main body and at least one cover portion that cooperates with the main body to enclose the articles. The envelope is receivable between the at least one cover portion and the main body of the shipping container and at least one of the first and second flap portions is affixable to an exterior surface of the container.