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.
Disconnect the USB cable, and then remove the memory card and external USB device.
Pull out the paper cassette.
Stand the printer with the control panel's button at the top.
Be careful not to trap your hand or fingers when standing the printer. Otherwise you may be injured.
Dampen a 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.
Do not leave the printer standing for a long time.
Connect the power cord.