The workflow will continue to the next step after pausing for the specified time. The "Pause" doesn't cancel the workflow.
John Bethray -
Since the Pause For action relies on the Timer Service job within SharePoint, when the server comes back up, it will essential check to see if the "pause" has been complete (so for your example, it will look at the time stamp and add 24 hours). If the workflow should have continued while the server was down (and you do not have another server to pick it up), then the workflow will pick up where it left off; no need to restart or cancel and restart.
If the server was down for a few hours, it does not add the outage time to the pause duration, it will simply run as normal.
Hope this helps!