Tabbed viewing, editing, and managing multiple Visio files in single Window: Tabs for Visio (is also named Visio Tab).
Once the software is installed, you can find a tab bar in Microsoft Visio as in Internet Explorer 8 and FireFox.
When you open or create a drawing file, there will be a corresponding tab in the tab bar. You can switch among drawing files just by clicking the tabs; double-clicking on the tabs will close the relevant drawing files, and double-clicking on the blank place of the tab bar will create a new drawing.
Save all files in the tabbed window by one click.
Open current document or workbook in new window.
Open the relevant folder of current document.
Close all files in the tabbed windows (a confirmation dialog box will appear when you choose to close all files).
Close other files (exclude current file) in the tabbed windows.