Below Simple step will help you to understand How do i reset my canon printer to factory settings...
Check if the Pixma printer is turned on.
Visit the Menu option and select Setup.
Make use of the navigation arrows to highlight the option you want.
Next, tap the Device Settings option and press the OK button.
Choose Reset Settings. Tap OK to initiate the reset process.
A few Pixma models will allow you to select the Device Settings option directly without going to the Setup menu.
If you are unable to reset canon printer then you can call customer support following the link over here to know about how to reset Canon printer?