Lines appearing on printed PDF output that don't show on screen point to either a printer hardware problem or a rendering issue in how the PDF is being sent to the printer. The nature of the lines โ horizontal stripes vs. thin rule lines vs. banding โ tells you which direction to look first.
Horizontal Stripe Banding: Almost Always a Printer Issue
Regular horizontal stripes across the printed page โ evenly spaced bands of lighter or missing ink โ are a classic sign of clogged print heads on an inkjet printer. The nozzles that jet ink onto specific horizontal rows are blocked, so those rows print with less ink or none at all. Run the printer's built-in printhead cleaning cycle (usually found in the printer software or settings menu) and print a test page. One or two cleaning cycles usually resolves banding.
If banding persists after multiple cleaning cycles, the printhead may need deeper cleaning or replacement. On laser printers, similar stripe patterns can indicate a worn drum unit or a low toner cartridge that's distributing unevenly โ replacing the affected component resolves it.
Thin Lines That Appear in the PDF Itself
If the lines are thin rule lines that appear at specific places on the page โ rather than evenly spaced stripes โ they may actually be in the PDF content. Zoom into the area in your viewer at 200-300% and check whether the lines are visible on screen. If they are, they're part of the document: table borders, section dividers, or thin graphic elements that are only visible at print resolution.
A common source of unexpected thin lines: hairline borders on table cells or text frames in the source document. These look like nothing on screen at 100% zoom but print as visible lines. If you have access to the source document, selecting the affected elements and removing or thickening the border solves it. For a PDF you've received, a PDF Editor can sometimes identify and delete these thin border elements.
Lines Caused by PDF Rendering and Tiling
Some PDF viewers, particularly browser-based ones, render pages in tiles โ dividing the page into rectangular sections and rendering each separately. When printed, the seams between tiles can appear as faint lines at regular intervals. This is a rendering artifact, not a printer problem.
The fix is to print from Adobe Reader rather than from a browser. Reader renders the entire page as a unified output rather than tiling, which eliminates seam lines. Go to File โ Print in Adobe Reader and use the standard print path rather than the browser's print function.
Transparency Flattening Producing Visible Seams
PDFs with transparency effects sometimes show faint lines at the boundaries of transparent objects when printed on certain devices. This is a transparency flattening artifact โ the printer's RIP (raster image processor) is handling the transparency calculation and creating visible seams at element edges.
Running the PDF through PDF Compression with optimization enabled sometimes resolves this by rebuilding the transparency structure before the file reaches the printer. Alternatively, printing at a higher quality setting or using PostScript output rather than standard PCL can eliminate the artifact on devices that support it.