When Microsoft released the Windows 8.1 update for Windows 8 operating systems some time back, users were able to download the and install the updated through the store. Unfortunately the below specified Windows 8 editions do not support the update from the store.
Windows 8 Enterprise. Talk to your system admin about updating to Windows 8.1.
Windows 8 Pro, if installed by an organization or a program that uses Volume Licensing. Talk to your system admin, or the administrator of the program that was used to install Windows 8. If you’re the administrator, you can find more info and links to Windows 8.1 ISOs in the Windows 8.1 Enterprise Evaluation.
Windows 8 Pro, if installed using an MSDN or TechNet ISO, and activated using Multiple Activation Keys. You might be able to download a Windows 8.1 ISO from MSDN or TechNet.
Windows 8.1 Preview or Windows RT 8.1 Preview. You might still be able to update from the Store. For more info, see Update from Windows 8.1 Preview to Windows 8.1.
If you have a Windows 8 Enterprise and you cannot find the Windows 8.1 update in the store, download the step by step guide form the below link. To achieve this you shall require the Windows 8.1 Enterprise DVD which can be downloaded from the Microsoft Volume Licensing Service Center
Windows Update Step by Step Guide http://1drv.ms/1r86qvq