Canon MX450 Series Online Manual page 792

Note
If the paper is rolled up and it is difficult to remove, grasp the edges of the paper, then
remove the jammed paper.
If you cannot remove the jammed paper from the transport unit, close the transport unit,
take back the machine in original position, then open the paper output cover to remove the
paper.
Paper Is Jammed inside the Machine
6. Close the transport unit.
Note
After you close the transport unit, take back the machine in original position at once.
7. Plug the machine back in and turn the machine back on.
8. Reload the paper.
All print jobs in the queue are canceled. Reprint if necessary.
If you cannot remove the paper or the paper tears inside the machine, or if the paper jam error
continues after removing the paper, contact the service center.