When paper is not fed from paper cassette correctly, clean the roller inside.
Turn off the printer by pressing the 
button.
Unplug the power cord, and then disconnect the power cord.
Open the scanner unit.
Make sure that the ink tank cap is securely closed.
If the ink tank cap is not securely closed, ink may leak.
Close the scanner unit and the ADF cover.
Slide out the paper cassette, and then remove the paper.
Stand the printer on its side with the printer's ink tank at the bottom.
Be careful not to trap your hand or fingers when standing the printer. Otherwise you may be injured.
Do not leave the printer standing for a long time.
Dampen a soft cloth with water, wring it out thoroughly, and then wipe the roller while rotating it with the cloth.
Return the printer to its normal position, and then insert the paper cassette.
Connect the power cord.