You do not typically download the ActiveX control as a standalone file. Instead, it is when you install the standard version of Adobe Acrobat Reader.
It sounds like you're highlighting a of Adobe Reader (or Acrobat) related to its ActiveX control download.
File > Save As Other > Reader Extended PDF > Enable More Tools File > Save As > Reader Extended PDF Acrobat Pro 8/9 Advanced > Enable User Rights / Extend Features Enabling Specific "Long" Content Features
If your goal is to handle long content or large files effectively within the ActiveX control, consider these specific settings: