Canon LBP7210Cdn Manual page 88

Be sure that the paper stack does not exceed the load limit mark lines. If the paper stack exceeds
the load limit mark lines, this may result in misfeeds.
Precautions when loading paper in the multi-purpose tray
Load the paper so that it is straight.
If the rear edge of the paper stack is not properly aligned, this may result in
misfeeds or paper jams.
If the paper is curled or folded at corners, flatten it before loading it in the printer.
If you use paper that has been poorly cut, multiple sheets of paper may be fed at
once. In this case, fan the paper thoroughly, and then align the edges of the stack
properly on a hard, flat surface.
NOTE
When printing paper with a letterhead or logo
See "Paper Loading Orientation"
Align the paper guides with the width of the paper.
IMPORTANT
Be sure to align the paper guides with the width of the paper.
If the paper guides are too loose or too tight, this may result in misfeeds or paper jams.
and load the paper in the proper orientation.