Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
I suggest that you try altering two things in the Settings for your printer, on your iMac computer.
First, locate any printer setting for 'high quality' or high quality printing, and set it to Draft, or even Normal, quality.
Second, locate a printer setting for 'print directly to printer' and enable it. This disables buffering of the print job, and makes printing quicker in many cases.
Or, it may perhaps be a setting called 'buffer printing' or 'send print job to buffer'. That would need to be disabled, if that is what the setting is called.
Let me know how it goes, and what you find, and what happens, please.