You can save room on your hard disk and reduce the time it takes to open a drawing by removing unnecessary information from your Microsoft Office Visio files.
Click File > Check for Issues > Reduce File Size.
If you're using Visio 2010, you'll find this under File > Info > Reduce File Size.
If you're using Visio 2007, on the File menu, click Remove Hidden Information.
Click the File Size Reduction tab.
Do one or more of the following:
Select the Remove preview picture check box to remove the preview picture from the file properties.
Removing the preview picture has no effect on the look of your drawing. However, if you remove the preview picture, you cannot see a thumbnail preview of the drawing in the Visio Getting Started window or in Windows Explorer.
Select the Remove unused master shapes check box to remove unused shapes from the drawing's document stencil.
When you start a drawing, Microsoft Office Visio creates a stencil, called the document stencil, that is specific to that drawing file. Each time you drag a shape onto the drawing page, the shape's master is copied to the document stencil, and an instance (or copy) of the master is created on the drawing page. If you later delete all instances of a shape from your drawing, the master remains in the document stencil. Removing that master reduces the drawing file size.
Removing unused master shapes has no effect on the look of your drawing.
Select the Remove unused themes, data graphics and styles check box.
Removing unused themes, data graphics, and styles has no effect on the look of your drawing. If you remove unused themes and data graphics, however, they disappear from the Theme and Data Graphics task panes. You will have to re-create them if you want to use them again.