I have firefox installed system-wide for all our users. Unfortunately the Adobe Reader Plug-in is rather flakey and doesn't work some of the time. As a result I want to disable the plug-in by default for all our users, but still allow them to enable it if they want via the standard Tools->Add-ons->Plug-ins menu option. How can I have this plug-ins enabled/disabled status be disabled by default?

I've been able to configure system-wide configurations before by setting preferences in the mozilla root folder file defaults/pref/all.js, but enabled/disabled plugins doesn't appear to be configured in the preferences.

[edit 1]: I found 'How to manage firefox plugins in pluginreg.dat file' which explained some of the formatting of the pluginreg.dat file. From there I could see flags are masked as follows (from nsPluginHostImpl.h):

#define NS_PLUGIN_FLAG_ENABLED 0x0001 // is this plugin enabled?
#define NS_PLUGIN_FLAG_OLDSCHOOL 0x0002 // is this a pre-xpcom plugin?
#define NS_PLUGIN_FLAG_FROMCACHE 0x0004 // this plugintag info was loaded from cache
#define NS_PLUGIN_FLAG_UNWANTED 0x0008 // this is an unwanted plugin
#define NS_PLUGIN_FLAG_BLOCKLISTED 0x0010 // this is a blocklisted plugin

But is there a way to add this to the defaults so that that NS_PLUGIN_FLAG_ENABLED is removed by default?