I want to select my printer in the Acrobat configurator properties, but I can't seem to find the drop-down to do this.
There is no drop-down to choose a printer because the Adobe Acrobat scripting API doesn't allow to specify the printer on a Mac.
If you want to use a specific printer, then you will have to change your default printer on the system. Keep in mind that the default printer will be the same for every flow.
On Windows, the function to select any installed printer is available so you can just select the printer that you need in that flow.