If you have an MSDN account, you may be able to upgrade from Windows 8 to Windows 8 Pro. First, login to http://msdn.microsoft.com and click on Access Benefits. Once there, click on Go To My Product Keys and scroll down looking for Windows 8 Pro. If you have a key available, grab it.
Next, open Control Panel (which you can get to quickly with Windows-x) and select Add Features to Windows 8. Enter the key you just got from MSDN and once verified, proceed with the uupdate.
Hey! Presto! Windows 8 Pro.