Cups printing command to Canon Printers asks for A4 paper even when everything is marked Letter

[Anonymous]

We have a Linux box with custom software for our industry on it.  The problem we are having is printing to our Canon printers it always defaults to A4 size even tho everything is marked letter.  When this happens we have to go over to the printer when it beeps and pick the letter draw for it to clear and print.  Any suggestions how to get around this?