Have you heard about TeamSpec ?
Team Spec provides rich team project artifact management directly inside Microsoft Office Word allowing specification, requirement, and other document content to maintain integrity with TFS (Visual Studio Team Foundation Server) content.
Most of the DEV teams are using Word as the primary tool for authoring requirements and then use TFS to manage them (thru work items). Team Spec offers a smooth integration between Word and TFS.
ex: TeamSpec enables you manage changes made to requirements in your document or on the Team Foundation Server, click to watch the video
For more information, please refer to the Team Solution web site.