Canon PIXMA TR4500 Series Online Manual page 79

3. Grab handle part of front cover and pull out cassette until it stops.
4. Use the right paper guide (C) to slide both paper guides all the way out.
5. Load the envelopes in the center of the cassette WITH THE PRINT SIDE FACING DOWN.
Fold flap of the envelope and load the envelope in portrait orientation with the address side facing down.
Push the envelopes all the way to the back of the cassette. Up to 5 envelopes can be loaded at once.
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