Hi Shoshanao,
As stated above you have Mac OS (El Capitain 10.11.6) and experiencing issues while installing the Adobe Reader.
Adding on to the discussion:
- Adobe Reader is not supported on Mac OS 10.11.6, you may have to update the system. For more information, you may please refer to the help article - Adobe Acrobat Reader DC system requirements
- For installing the Adobe Reader on Mac OS you may please follow the help article - Install Adobe Acrobat Reader DC on Mac OS
Let us know if you need more information.
Regards,
Amal