To promote the discard of documents made unnecessary with document updates.

A server 10 receives and stores document data (including a document ID) created by a client, access rights (client IDs associated with the document ID) and the like, and sends a document registration notification to clients (destinations) having an access right. When requested to send the document data by the client having an access right, the server 10 sends the document data. When receiving updated document data from the client having an access right, the server 10 stores the updated document data and sends a document update notification to the destination clients.