An open-source project I am working on uses Visio drawings for documentation, which are checked into source control. For those working on the project who don't own Visio, we have been converting the vsd files to PDFs so that they can still view them. It's not too difficult to save a copy as a PDF when making changes to the documentation, but we would like an automated way to do this conversion, so that we can set it up as a pre-checkin script in the SVN client. If anybody knows of a way to do this, either using something built-in to Visio, or with an outside script or command line tool, we would appreciate it.

Edit: Thanks to the suggestion below, I have found the Visio Viewer 2010. This will be helpful for our contributors using Windows. We would still like to have the ability to create PDFs though, as there are readers available on every major operating system, and our contributors will not be using only Windows.