How to change from Evaluation to the real stuff in Windows Server 2012 R2

Yes it is possible to perform with no strange tools at all. Before you start you need to have your product key (either a MAK or a KMS client key)

Step-by-Step

• Start an elevated command or powershell prompt.
• Execute “slmgr /dlv” to get information on the current status.

• Execute “dism /online /get-currentedition” to get the current edition, it should be an Evaledition

• Execute “dism /online /set-edition:ServerStandard /productkey: /accepteula”
• The key in this case is the KMS Client key for Windows Server 2012 R2 and you can get all those keys from
  http://technet.microsoft.com/en-us/library/jj612867.aspx

• Restart the server (it will reboot twice)
• Done