A document management system records an operation history associated with an electronic document. When output of a document is instructed, it is determined whether an output history associated with the document exists in the recorded operation history. When it is determined that the output history associated with the document exists, a user is informed of the fact that the document has already been output, who output the document in the past, and when the document was output. The following operation errors can be prevented. That is, a specific document is repeatedly output by a plurality of users, and each operation is repeatedly performed.