Install Adobe Reader DC without uninstalling Adobe Reader?
Are you talking about Acrobat (Pro) or Adobe/Acrobat Reader?

In the second case, you would not get the "official" download file from Adobe (because that is just a (IMHO extremely crappy) install manager. Instead you would get the actual Reader installer from the enterprise page of the Adobe website

As you are on Mac, multiple versions can be installed in parallel, and even do run concurrently. Under Windows, neither is possible; all which is possible to install one version each of Reader and Acrobat, and preferably the same (Acrobat DC and Reader DC).