You may find that since upgrading to Windows Server 2012, Print And Document Services (Print Server), users are now prompted for administrator credentials and are not able to install some printer drivers without admin rights. This is because Windows Server 2012 doesn’t support unsigned Type 3 (user mode) printer drivers (printer drivers without a signed certificate from the supplier of the printer driver).
What are Type 3 (User Mode) printers? User mode printers are printer drivers that run in the user context, instead of Kernal Mode printer drivers which run in the context of the Windows machine. This means that if the printer driver crashes, it only affects the user for which the driver crashed.
To fix this and enable users to install unsigned printer drivers, you need to change the following group policy to Configure Security Prompts.
Computer Configuration -> Policies -> Administrative Templates -> Printers -> Point and Print Restrictions
This is because by default, Windows 2012 Print Server disallows users to install unsigned printer drivers to their machines without admin rights.