very common problem. Cleaning would be first step. second make sure your rollers are free of debris. If you are still using a laser printer change the toner cartridge as this changes the drum in most cases. If its an ink jet. Clean everyday take it in for a professional cleaning. However I have found that once you start getting the lines they will probably be around intermittently till such time as it becomes such a problem that you purchase a new printer. Most of the printers we use are not really manufactured for commercial use and even though new cartridges mean new print heads. The parts that are permanent to the machine don't wear very well. It's the nature of modern equipment no one want's to pay for someone to build a durable printer that's probably going to be obsolete in 3 years or less anyway.