Due to a decimal point error on the A5 paper size. A5 paper is not detected as A5.

to resolve this we create a new paper size with the correct dimensions.

steps will be similar for other canon printers.

Step 1: in "Devices and Printers"

Step 1 screenshot. 

Step 2: "Canon LBP6230/6240 Printing Preferences"

Step 2 screenshot. 

Step 3: left click on "Page Setup (tab item)" in "Canon LBP6230/6240 Printing Preferences"

Step 3 screenshot. 

Step 4: left click on "Custom Paper Size... (button)" in "Canon LBP6230/6240 Printing Preferences"

Step 4 screenshot. 

Step 5: left click on "A5 (text)" in "Custom Paper Size Settings"

Step 5 screenshot. 

 

Step 6:  "Width: (edit)" in "Custom Paper Size Settings"

Step 6 screenshot. 

Step 7: change width to 148mm;Rename paper 'A5 custom'

 

Step 8: left click on "Register (button)" in "Custom Paper Size Settings"

Step 9: left click in "Custom Paper Size Settings"

Step 10:  left click on "Apply (button)" in "Canon LBP6230/6240 Printing Preferences"

Step 11: left click on "Canon LBP6230/6240 Printing Preferences (dialog)" in "Canon LBP6230/6240 Printing Preferences"