How can I install the Adobe Reader DC without uninstalling the old Adobe Reader (11)? I want to manage the installation of Adobe Reader DC on my clients without deleting their old Adobe Reader. Is there a official download site from Adobe or could I edit the .pkg package? I got a free Adobe Enterprise License also but I can only find the installer at Adobe which installs the DC but uninstalls the old 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).