Adobe has ended support for Adobe Reader XI and Adobe Acrobat XI on October 15, 2017.
This means you neither receive technical support nor product updates or bug fixes or security updates for Adobe Reader and Adobe Acrobat.
Adobe Reader XI and Adobe Acrobat XI reaches End of Life
If you’re using either of these, its high-time for you to uninstall and get Adobe Acrobat Reader DC or Adobe Acrobat DC other third-party PDF Readers such as Foxit or Sumatra PDF for your PDF viewing needs or you can use built-in PDF Viewers offered by Chrome, Edge or Opera browsers
.