A system includes an image forming apparatus, a first document server apparatus, and a key server apparatus, the image forming apparatus being configured to determine whether document data is private or public, when the document data is determined to be private, then determine a level accessible to the document data, and transmit level information indicating the level and the document data to the first document server apparatus, the first document server apparatus being configured to receive the level information and the document data from the image forming apparatus, generate a document ID for identifying the document data, store the document data in association with the document ID, transmit the document ID to the image forming apparatus, determine an accessible user ID that identifies a user accessible to the document data based on the level information, generate a public key and a private key used to encrypt the document data.