Canon iX7000 Series On-Screen Manual page 36

Loading Paper in the Rear Tray Page 36 of 468 pages
Important
Always load paper in the portrait orientation (B). Loading paper in the landscape
orientation (C) can cause paper jams.
Slide the Paper Guides (A) to align them with the both sides of the paper stack.
(4)
Do not slide the Paper Guides too hard. The paper may not be fed properly.
Note
Do not load sheets of paper higher than the Load Limit Mark (D).