Can I start downloading on a fixed schedule, e.g. every weekday at 7 AM, as that's just before I go to work?
As a free user, your best option is to go to Settings > Downloads > Subscriptions, and set [Auto-download] to [Wi-fi and charging]. After which, set a short refresh interval like 1 hour in Settings > Connection and Account > [How often to update]. Meanwhile, when you upgrade to premium, you'll be able to set more specific sync schedules.
For advanced users, you may consider using the Android intents we support for sync and download control, with a third-party app like Tasker.