Installing Adobe Reader is a two-step process. First you download the installation package, and then you install Adobe Reader from that package file.
If you are on a Windows computer, see Install an older version of Adobe Reader | Windows.
Before you install, make sure that your system meets the minimum system requirements.
Firefox: Download and install Reader
Safari: Download and install Reader
To see if other users are experiencing similar download and installation problems, visit the Acrobat Reader forum, or the Deployment & Installation forum on AcrobatUsers.com. Try posting your problem on the forums for interactive troubleshooting. When posting on forums, include your operating system and product version number.