Adobe has removed the download links for the Acrobat 9 updates from their web pages. Possibly because Acrobat 9 is officially no longer supported.
But there are many users stilling working successfully with Acrobat 9.
Sometimes a new installation is required which means installing Acrobat 9.0.0 and all incremental updates. Unfortunately the menu Help > Check for Updates… does not always work proberly.
Fortunately one can still download the updates from the Adobe FTP server: