When I select a file in the solution explorer, it opens right on the preview tab.

For many file types, this is a useful feature. But when adding PDF files to the site, this is not so. How do I configure the Visual Studio 2012 Preview feature so that it does not view PDF files?
(NB Kyralessa shows how to disable the preview function in answer to another question , but I would like to leave it at all and disable it for PDF files.)
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