I could not open the PDF. Acrobat says there's an error in the file. Hence I cannot check the spacing between the lines. That spacing, divided by 3, gives the approximate diameter of the roller that's causing the problem.
However, most likely it is a fault in the printer's drum. You can fix that by replacing the toner cartridge. The drum is part of the catridge; it's the green roller you will see when you lift the flap on the cartridge. When you lift the flap, have a look at the roller, to see if you can spot any problem. You can turn the roller by hand by moving the gears. Do not touch the roller itself as that may leave marks on your prints. The drum is light-sensitive, so don't leave it exposed for too long.
