Firefox 3.6, open pdf outside of browser

[stan]

When Firefox updated to 3.6 in F14, for some reason pdfs now open
inside the browser.  I don't like that behavior and would like to
change it, but can't find anything definitive about how to do that.

I use whatever the default pdf viewer is, and I think what I have to
find is the configuration for that viewer, either in Firefox or itself,
and tell it to open external to the browser.

Can anyone tell me how to do this?