The sheets print fine, but once you tape them together a thin white line runs along some of the seams. It is most visible on dark or photographic posters, and it is not a printing defect.
Why it happens
Without overlap, you cut each sheet on its cut line and butt it against its neighbour. Every seam then depends on a perfect cut and perfect placement. A cut that lands a millimetre inside the line leaves a sliver of bare paper, and bare paper reads as a white line against the image.
Nothing is missing from the export. The gap is the paper you did not cut away.
The fix — turn on overlap
Overlap prints a strip of the neighbouring tile's content into the margin band, so a slightly short cut lands on duplicated image instead of blank paper.
Options are Off, 25%, 50%, 75% and 100%. Start at 50%.
The amount is a fraction of the margin, not a length
This is the part that catches people out. Overlap is measured as a percentage of your margin, not as an absolute distance.
If your margin is 0, your overlap is 0 — no matter which percentage you select. Set a margin first. 0.50 in is a good starting point, and it also fixes cropped pages.
At a 0.50 in margin, 50% overlap gives you a 0.25 in strip on the left and top edge of every interior tile.
Why not 100%?
100% runs the strip all the way to the physical paper edge, which most consumer printers clip — the same unprintable border described in the cropped pages article. It is deliberately not capped, because borderless printers exist and the choice is yours. But it is not the value to reach for first.
How to assemble sheets that have overlap
Strips are printed on the left and top edges of each tile — the side opposite the scissor marks.
- Cut sheet A on its right-hand cut line.
- Lay sheet A over sheet B — B being the sheet immediately to A's right.
- B's left-hand strip sits underneath A and fills any gap left by the cut.
Work left to right along a row, then top to bottom down the rows, always laying the earlier sheet over the later one.
The outer perimeter of the poster gets no strip: the first column has no left neighbour and the first row has nothing above it. That is expected, and those edges are trimmed to the poster boundary anyway.
Overlap is a paid feature
Overlap requires a Pro or Pro+ plan. Setting it on a free account reverts it to Off and opens the upgrade prompt, so it is worth knowing before you plan around it — see pricing.
Everything else on this page, including the margin, is available on every plan.