Caution: Avoid third-party "download manager" sites. They often bundle adware. Always verify the digital signature of the file after downloading.
Adobe Reader XI (11.0.23): A Look Back at the Final Classic Version adobe reader xi 11.0.23 download
Unless you are running Windows XP on an air-gapped machine, you should install the current Adobe Acrobat Reader DC (or a lightweight alternative like Foxit or SumatraPDF). Using Reader XI on a modern, internet-connected PC is a significant security risk. Caution: Avoid third-party "download manager" sites