I upgraded to Big Sur, now my canon prixma pro 100 won't print. can I upgrade my drivers ??

Hi,

Yes, your printer, Canon PRO-100, is mentioned in About AirPrint - Apple Support as a model supporting the driverless AirPrint technology. This means that it can be used with macOS without having to install drivers, if the printer is connected to a network (Wi-Fi router), the same network (subnet) as the computer. See the AirPrint guide at https://www.canon.co.uk/support/consumer_products/apple_airprint_guide/ for details.

https://www.usa.canon.com/internet/portal/us/home/products/details/professional-large-format-printers/professional-inkjet-printers/pro-100

If connected via USB, drivers will be needed.

https://www.usa.canon.com/internet/portal/us/home/support/details/professional-large-format-printers/professional-inkjet-printers/pro-100/pixma-pro-100?tab=drivers_downloads

(select the operating system macOS Big Sur v11.0 in the menu, not macOS 11).

Reset the Mac printing system to solve a problem - Apple Support

Add a printer on Mac - Apple Support

EDIT: Just noticed that Allan Jones already had posted the driver download link.

Look under System Preferences > Software Updates for any new drivers.

The image is from Mojave but the system updates for Big Sur should be in the same place.

If they are not there, you need to ask Cannon. It is their duty to stay current with newer OS versions.

EDIT: This Canon page shows a driver for that model that claims to work with Big Sur. It was released in December 2020:

https://www.usa.canon.com/internet/portal/us/home/support/details/professional-large-format-printers/professional-inkjet-printers/pro-100/pixma-pro-100?tab=drivers_downloads