I do not like to open the pdf files inside the browser. The reason behind is that :

• by opening the pdf file it takes me away from the page. I may want to open the pdf and also simultaneously have a look at the page.
• I think the whole thing becomes a bit slow sometimes …
• Also evince is such a nice document viewer which is a native of my Linux distribution (Fedora) and evince is much more fast than acroread.

any way ….. other people may have their own reasons too …. So here is what I did to disable the Acrobat Plugin :-

# locate nppdf
/opt/Adobe/Reader8/Browser/intellinux/nppdf.so
/root/.mozilla/plugins/nppdf.so
/usr/lib/mozilla/plugins/nppdf.so
# rm /usr/lib/mozilla/plugins/nppdf.so

i. e. removed the file named nppdf.so from your Mozilla plugins folder.

Enjoy …..