These are the official direct download links to Windows 8.1, Windows 8, and Windows 7 language packs.
How to Install Language Pack on Windows 8 or Windows 8.1
For Windows 8.1 and Windows 8, rename the file to .MLC instead of .CAB and double-click to execute.
You can also obtain these language packs through Windows Update or Language Control Panel in Windows 8/Windows 8.1.
Note: If you install a language pack on Windows 8 and then upgrade to Windows 8.1, you will need to reinstall the language pack. Language packs are specific to the Windows version so you cannot install a Windows 7 language pack on Windows 8, etc.