A network device such as a server monitors user behavior and provides subscriptions to documents based at least in part on that behavior. Subscription triggers include requesting at least a predetermined percentage of the entire document, requesting at least a predetermined number of pages in a document, and requesting a document at least a predetermined number of times. If documents are organized in a root and branch structure, the subscription may be triggered based on the extent to which documents are requested in the structure, e.g., triggered upon request for a branch document related to a root document. Subscriptions may also be limited to a portion of a document, such as a branch document associated with a root document.