Open and install the AdbeRdr11010_en_US.exe file.
For everyone else:
Adobe ended official support for Acrobat Reader XI on October 15, 2017 . Version 11.0.23 is a final patch released before that end-of-life (EOL) date. Consequently, it does not receive new security updates. Proceed with caution. adobe acrobat reader xi 11.0.23 download