Office is onlt part of a Windows 8 RT install on devices such as the Surface.
Office is a separate product to Windows in all other cases.
The 'My Documents folders have been a part of Windows since Win95 - but are merelt a defined storage are for data, not part of Office.
If you want Windows 8, your best option is to run the Windows 8 Upgrade Assistant which will take youm through the whole process from checking your current system's ability to run Win8, which version is best for you, the purchase, download and install. Windows 8 upgrade offer - Windows 8 special offer Upgrade to Windows 8 - Microsoft Windows