Migrate to DHCP from a static IP network

We are currently running an all Windows Environment. We use static IP. We are thinking about setting up DHCP on our Domain controller. If some of the PCs or Copiers are set to static IPs when I enable DHCP, will DHCP try to assign that IP or will it see its being used? I’m not sure if I have to reserve IPs that I plan on keeping static. Thanks