I am actually still using CS5 at home. Recently I’d updated to a more recent iMac and found it impossible to re-instal Design Premium. Was using the official disk image – freshly downloaded from my Adobe account.

This was the pesky error message:

“Install.app” can’t be opened. You should eject the disk image.

The solution is simple – as (finally) outlined by Adobe in their help docs here: Installing Creative Suite on macOS 10.12 (Sierra):

Launch the installer binary from the command line.

  1. In the Finder right click on the Install.app and select “Show Package Contents”
  2. Navigate to Contents/MacOS/install
  3. Drag this binary onto a blank Terminal prompt and hit enter.

Follow the link above from more info from the nice Adobe folks.