Sanity Clause wrote:

Preventing plugun scanning will (I think) disable the use of the
plugins in Firefox.

Nope.

Yup.

You say no, but you really haven't disabled plugin scanning, so you
wouldn't know.

If you set plugin.scan.plid.all to false, then you'd be disabling plugin
scanning, and then you'd see that none of your plugins are available /
functional.

plugin.scan.Acrobat, plugin.scan.Quicktime and
plugin.scan.WindowsMediaPlayer are the minimum versions that Firefox
will accept and use. Versions older than that will not be used and will
not show up in the Add-ons Manager, Plugins category.

changed plugin.scan.Acrobat from "5.0" to "9"

I believe that particular change will result in Firefox NOT
opening Acrobat Reader (AR) if the installed version of AR
is less than 9. So in effect you disable AR with that setting
if you have AR version 6.

I do indeed have version 6.0.6.401, and PDFs open just fine
(I tested) either *in* Firefox, in an external "instance"
of AR, or even in Foxit.

Changing plugin.scan.Acrobat to something higher than 6 has nothing to
do with whether or not you can open PDF files in Acrobat Reader or any
other PDF reader.

That setting only controls how (or if) Acrobat Reader is opened within
the browser window when the browser encounters PDF material on a web
page. If you have your browser configured so that it asks you what to
do with .PDF files (ie - save or open) then the setting
plugin.scan.Acrobat has no effect on that behavior. If the browser is
set to automatically open and display PDF files without asking you, then
that setting becomes relevant.