Free Visio Viewer software (version 1) is a tool that allows users to view and open Visio files without the need for Microsoft Visio. The software supports all Visio file formats, including VSD, VSS, VST, VDX, VSX, and VTX. It enables users to zoom in or out of the diagrams, rotate pages, and navigate between pages. The software also provides a simple and easy-to-use interface, making it accessible for users of all levels.