I just purchased one of these printers. I was testing printing envelopes, which was one of the main reasons I purchased the printer. I noticed that when setting the paper size to the Commercial D10 envelope (4.125 x 9.5) preset in the Word (using the driver preset entry) and registering the same preset entry from the paper tray, a 1.14" left hand margin was enforced by Word. This caused the return addresses to print in the wrong location, as the margin requirement would not let them be aligned close to the left edge of the envelope.
This seems a problem with the preset. I defined a custom envelope of 9.5 x 4.5 size from Word and registered custom envelope on the printer. Although the paper size shown in Word was larger than the actual envelope, I was able to get the printer to print the envelopes correctly after adjusting the vertical locations of the text blocks. So this does not appear to be a mechanical or feed problem with the printer.
Is the commercial D10 preset broken in the driver, or are there other settings I've missed? The driver I'm using is the current one the Canon website as of July 3, 2015. I am printing by wired Ethernet. I found one other person having this problem on the Microsoft forums, but they were unable to address this problem.