The first thing you must have in place is a new Windows Server 2012 R2 server with the Printer and Document Services server roles installed. When you have installed this role it requires a rebooted before the Printer Manager option appears under Tools from Server Manager. Open Printer Manager and right click on Printer Manager and select Migration Printers...
Select Export Printers Queues and Printer Drivers to a File, click Next.
If you are backing up the configuration of your old print server use the Browse button to select this server here and click Next.
On the review page also click Next.
Set a local path as a destination for the exported files containing the old servers printer configuration, click Next.
Click Finish when the export completes.
Now return to Printer Management and right click and choose Migrate Printers... again, now choose Import Printer Queues and Printer Drivers from a File, click Next.
Point to the configuration file that was generated in the previous steps.
As this server is going to host the printer ensure This Print Server is selected and click Next.
In the Import Mode field configure it to Overwrite Existing Printers and for List in the Directory to Don't List Any Printers, click Next to continue.
Now create a new GPO and expand User Configuration\Policies\Windows Settings\Deployed Printers, right click on the white space and select Printer.
Use the Browse button to point to the new printer server, with attached printers, use the Add button to move them across.
Now in the same GPO you can use Group Policy Preferences to delete the old printers, expand User Configuration\Control Panel Settings\Printers and right click and choose New. From there under Actions select Delete and enter the Share Path of the old print server/printers.
Perform a GPO update on a client and you will notice the old mapping have been removed and the printers have been re-mapped from the new print servers.