We have Canon MFDs. Sometimes a paper size gets set to A4 instead of letter and when it is sent to the MFD to print, the MFD pops up a "paper out" message (because we have no A4 size loaded, obviously). Students come to the desk and say, "The printer is out of paper," when it really isn't -- we have to show them how to select letter size for the job and then it prints fine.
Someone at the conference told me they were able to get the A4 size to go automatically to the default paper size (letter) on Canon copiers without intervention. (Sorry, I did not get your name. I was so excited that this could be done, I just forgot!) So, if the person I talked to or anyone else knows how to do this, please contact me (email@example.com). Our Canon service tech said he did not know of a way to do it and I spent time this morning going through every imaginable setting to find this and I could not either.