In case you missed the announcement, the Visio team has announced the availability of the Microsoft Visio Viewer on their blog.The Microsoft Visio Viewer is a free download that lets your users view Visio drawings without having Visio installed on their computer. This download is also useful for users of earlier versions of Visio who share Visio files with users of Visio 2013. As you may have heard, earlier versions of Visio can’t open Visio files that use the new VSDX file format. We are aware of the issue and are working on an update to Visio 2010 to address this issue. Until then, we recommend that you deploy the new Visio Viewer to users who need to view VSDX files but who don’t have Visio 2013. With the viewer installed, these users can also preview Visio files from Outlook and Window Explorer. Check out the Visio blog for more details.
Update: Visio 2010 users can now download the Visio Compatibility Pack from the Microsoft Download Center. The Microsoft Visio Compatibility Pack lets Visio 2010 users open files created in the newer Visio 2013 drawing file format (files with a .vsdx and .vsdm extension). The Microsoft Visio Compatibility Pack opens drawings in the newer file format when used together with the Microsoft Visio 2010 SP2 update.