Plugins for Adobe Acrobat XI Pro. Where are they??

In Adobe Acrobat XI Pro Software on the menu bar open Help > About Adobe Plugins.  A list of installed and/or available plugins for the program are displayed and marked certified.  However, several of the plugins listed are also listed as not installed.  It appears plugins are downloaded by default during initial installation since I hadn't actually contributed to the list's contents.  There doesn't seem to be a way manage plugins?  Where are these missing plugins and how do I install them.  Please advise only if you know the answer. I am running Win7 64bit.