You can download the Free Microsoft Office Plugins and the Free Lite SDK from here.

Microsoft Office Plugins

Microsoft Word Plugin – Free Microsoft(c) Word Addin for Microsoft Word XP or Later.

Microsoft Excel Plugin – Free Microsoft(c) Excel Addin for Microsoft Word XP or Later.

Software Development Kit

Lite Software Development Kit – SDK Lite (Requires .NET) Please note that this is not the full SDK. The full SDK comes with the Developers Pack.