Hi, Bryan. Rohit's answer is correct.
You may also want to make sure that your scheduled emails are still scheduled in the future of when you deactivate and then reactivate your campaign. Another best practice is to add any additional Contacts to a Wait step placed right before the email you want them to start on. As long as your defaults are checked as "only allow emails to send to a Contact once" you should not have any resends to overlapping Contacts.
If you're an All Access Education Pass holder, you can take a look at these 5-minutes QuickCasts:
New Course - QuickCast: Moving Contacts in an Active Campaign [5 minutes]
New Course - QuickCast: Adding Contacts to an Active Campaign [5 minutes]
Hope this helps,
Clementina