How do I turn off ALL subscriptions on a 2008 Reporting Server?
The subscription process starts with the Jobs firing and inserting a row in the event table. So disable all of the subscription jobs. The ScheduleID in the ReportSchedule table in the ReportServer database is the job name. The category for the subscription jobs is Report Server.
On 2016, the ability to disable subscriptions was added. Not that it does you any good but someone is likely to mention that.
Sue