I looked there, but that seems to only apply to actually saving it -- whether Firefox should save the file, or open it in the selected application. I set PDFs, for example, to be always saved. Even if the PDF icon is shown (sometimes it isn't), double-clicking the link will still start Writer.
Edit > Preferences > Applications would be my guess.
2009/9/14 Chakat Sandwalker <firstname.lastname@example.org>:
> For some bizarre reason, when I save something in Firefox, such as a
> picture or PDF, if I double-click the item in the Download Manager it
> starts OpenOffice Writer to open the file. It's starting to get quite
> annoying. Does anyone here know how to get the correct programs (Eye of
> Gnome for pictures, Evince for PDFs, etc) to open the files instead of