If your printer is printing lines, it could be due to clogged nozzles, low ink levels, or misaligned print heads. To fix it, first, run the printer’s self-cleaning cycle, which is usually accessible through the printer’s software. If the problem persists, check the ink or toner levels and replace them if necessary. Align the print heads using the printer's maintenance tools. Ensure you're using the correct type of paper and that the paper is loaded properly. Finally, update your printer drivers. If none of these solutions work, consult the printer’s manual or contact customer support for further assistance.