Canon C9075 PRO Operating Manual page 48

If you want to load paper into the lower tray:
☐
Load the paper face up.
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4
Select the desired paper size → press [Next] .
Select the same paper size that is loaded in the Document Insertion Unit.
To select an A or B series paper size, press [A/B-Size].
5
Select the desired paper type → press [OK] .
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Document Insertion Unit-H1 (Optional)