Where do I download a Windows Server 2012 R2 .iso from, for use with Hyper-v?

Hello,

Where do I download a Windows Server 2012 R2 Standard .iso from, for use with Hyper-v?

The only official download I can find is the evaluation version from here:

http://www.microsoft.com/en-us/evalcenter/evaluate-windows-server-2012-r2

Is it recommended to use the evaluation version and then license it to make it a full version, or is there a better official download?

Thanks

Paul