Hello Matt. I also own a Canon printer, and I just got mine working again a few hours ago. Let me tell you how I did it. I bet my story will get you on the road to getting your machine working properly again soon.
Today I had to do some print jobs for an important meeting tomorrow. One document in particular had to be printed from my 2017 27" 5K iMac running Mojave 10.14.3, being as I didn't have a hard copy on hand to make a copy from. My printer is a Canon PIXMA MG7720. The printer itself continues to work fine, but as soon as I tried to print that one document from my iMac, I ran into trouble. My first problem was that the window insisted that my printer wasn't even connected to my network. Wonderful! Not really!
Well, after fiddling with it a bit and trying to get it working via both Wi-Fi and ethernet, I finally managed a connection via Wi-Fi. But wouldn't you know it! That wasn't quite the end of my troubles. I repeatedly tried to print the document, but the printing queue kept saying that it couldn't open the "PPD" file. That stands for "Postscript Printer Description" file, in case you didn't know it.
Then I had a revelation. Even though I already had the Apple Canon Printer Drivers 3.4 from last December installed , with so many people having printing issues with Mojave, I wondered if Canon might have some newer drivers on their website. So off I went. As it turns out, I found package installers for a newer printer driver, a newer scanner driver, and newer versions of all of the other utilities which comprise the Canon Utilities package. So, I downloaded everything -- seven files in all -- installed them all one by one, and then I rebooted my iMac. Then the moment of truth arrived. I reopened my document in the "Preview" app, and hit the "Print" option under the "File" menu. And lo and behold, the document printed without a hitch. Boy, I was so relieved!
So, while I obviously can't guarantee that this will work for you, I suggest that you visit Canon's website, and look for new printer and scanner drivers for your particular printer, along with updaters for the Canon Utilities package.
I hope that you found the above helpful, and that it leads you in the right direction for getting your own printing issues resolved. Please do let me know. Thanks!