Hi. You are not going to find 8.5x11 as an option on the printer's panel. Please look for LETTER size instead. Letter-size is considered 8.5x11 inch.
When you pull the paper cassette out and push it back in, the screen will ask you if you want to register the cassette. Please press the OK button for that message.
When you see the SIZE option, please use the ARROW buttons (triangles that point right or left) to find "Letter." Then, press the OK button. After that, please make sure that the correct paper type is selected and press OK.
You'll find information on registering the paper at the following link:https://support.usa.canon.com/kb/index?page=content&id=ART171610
Once the paper size and type is properly registered at the printer, please make sure that the print settings on the computer match the paper size and type that is loaded. Then, you should be able to print on letter size paper.
I hope this helps. Thanks for choosing Canon.
