From Detong Technology:
Tabs for Word (original name is Word Tab, Document Tabs for Word) add tabbed browsing and editing to Microsoft Word 2010, 2007 and 2003. This office add-in shows a tab bar in Word and creates a tab for every document opened in Word.
With Document Tabs for Word, you can handle multiple documents open in different windows easily. The tabs added by this Office add-in are configurable. Document Tabs for Word allows users to easily show/hide these tabs in Microsoft Word, to customize the tabs' color, appearance and position. Document Tabs for Word provides instant previewing for these customizations and configure changes in its Setting Center. Document Tabs for Word allows the user to place the tab bar on the above/below/left/right of workplace.