Canon imageCLASS MF4270 Basic Operation Manual page 70

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When setting paper, gently insert the paper into the multi-purpose tray with
the print side up.
When you load paper with a logo on, position the paper with the print side up (logo side) and insert it
so that the top of the paper feeds first in the multi-purpose tray.
When setting an envelope, gently insert the envelope into the multi-purpose
tray with the print side up and the right edge (i.e., closer to the stamp) first.
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