Canon BJ-200ex - Manual (Page 35)

§ If the print density of your page is very high, light paperstock
may curl slightly due to the large amount of ink. If you need to
print heavy graphics, try printing on heavier stock.
§ Do not use thicker paper than meets the specifications for this
printer. Printing with a paper that is thick enough to come in
contact with the print head nozzles may damage the print head
unit.
For complete paper specifications, see Appendix A,
Specifications.
Before Loading Paper
To ensure trouble-free paper handling, you'll want to set the
paper thickness lever and paper selection lever before
loading paper.
Setting the Paper Thickness Lever
You use the paper thickness lever to adjust the distance
between the print head and the paper to accommodate
different paper thicknesses. This distance is called the print
gap.
Set the lever according to the thickness of the paper you are
using:
§ Left is for printing on normal paper or transparencies.
§ Right is for printing on thick paper or envelopes.