I installed Adobe Reader 7.0 for Linux about a month ago while I needed to open a pdf document that required document authentication from its origin server. The document was successfully opened, but my Firefox browser could not open any pdf document anymore. Firefox was able to open pdf document using previous Adobe Reader version, but not Adobe Reader 7.0 for Linux. Mozilla website confirms this problem. However, I finally manage to get my Adobe Reader 7.0 for Linux works with Firefox and here is what I did.
After I have my Adobe Reader 7.0 for Linux installed and working, it is necessary to install the plugin part. To install it, just run this file
<install directory>/Adobe/Acrobat7.0/Browser/install_browser_plugin and will ask you whether you want to install it using global installation or user-specific installation. Choose option 1 (global installation). The next question is where to put the plugin file. Answer the question with the existing directory
Restart you browser and you’re done.