Whenever I have to install or update Adobe Acrobat, I always have to go back in afterward and remove the Acrobat plugin from the Library/Internet Plug-ins
directory. With the most recent update to Acrobat Reader 9.1, I spotted a new option. I was able to uncheck this plugin. Thank you Adobe for giving me this option. Preview is just fine for me for 99% of my needs.
Adobe Acrobat Pro is even worse. It asks you for the MS Office Toolbar and for the PDF Printer. After you say no, it asks you again about the Safari Plug-in. Then you still have to quit Safari to complete the install even though you are not using the plug-in.