Firefox, and all other browsers as well, offers two methods to display pdf documents. The first displays the pdf file in firefox itself and uses the Adobe Reader plugin to do so. The second method would start the Adobe Reader itself and display the pdf file there. The first method might be convenient but has some disadvantages that I would like to address.
The most obvious reason is load time. It takes some seconds to load the plugin. This by itself would not be a real problem but it locks the whole browser while loading. You can“t do anything besides waiting for the plugin to load and initialize. If an error occurs during this process the browser might lock up completely and might even crash. This happened to me before and this is really annoying.
My suggestion would be to change the firefox settings to the second method. To do so click on tools, options. Select the download tab and click on view & edit actions. Scroll down to PDf and select change action. Chose open them with default application instead of use this plugin.
You can use this method for other files as well. Look at all the quicktime file associations, they use the quicktime plugin as well. They should load faster if you switch to the quicktime application instead.

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Great idea. PDFs can be a nightmare. My “view & edit actions” window doesn’t contain any file extensions to modify! Any ideas why this is the case? I’m guessing one of my extensions may have disabled it.
I think you did not click change action, can that be the case ?
No, that option isn’t even available because there are no file extensions (PDF or anything else) to change the actions for.
now that is really strange ;)
And do not forget to consider the “Foxit Reader” as an alternat5ive to Adobe Acrobat: it is so much faster (practically immediate pop-up!), no comparison!
http://www.ghacks.net/2006/08/08/lightweight-alternatives-to-heavyweight-programs/