Canon imagePROGRAF PRO-300 13" Photographic Inkjet Printer - Manual (Page 588)

Back of Paper Is Smudged
Check1 Check paper and print quality settings.
Printout Results Are Unsatisfactory
Check2 Perform bottom plate cleaning to clean inside of printer.
Cleaning Inside the Printer (Bottom Plate Cleaning)
Note
• During too much printing, ink may stain the inside of the printer.
588