Can anyone point me to some documentation about the "Suspend activity"? The only argument the activity has is a string type reason field. That's it.
How do I tell the workflow where it has to resume once it suspends at a specific point?
I don't think the SharePoint 2013 workflow framework support Resume activity.
Only the core Windows Workflow Foundation supports Resume activity. However there is an alternative.
You can create State Machine Workflows for SharePoint 2013. Basically define states like 'InProgress', 'Review' and 'Finished' and implement an event handler to keep the workflow in 'InProgress' state based on the actions made to SharePoint list item/document