Poster splitter

No. The image or PDF is opened directly in your browser with the FileReader and canvas APIs; splitting and PDF generation happen on your device. Nothing is transmitted to a server — the site has no backend to send it to.

On a Mac, many people have reported this since macOS Sonoma (2023): free Reader shows Poster (and Advanced Print Setup) greyed out, and Adobe’s forum threads were still without a fix in 2025. Unticking "Print as image", the old advice, reportedly does not help there. Open the PDF here instead: choose the finished poster size and the sheet size, and the splitter builds a new PDF of tiles with overlaps and cut marks that any PDF reader prints at 100%. On Windows, Reader’s Poster option normally works — make sure "Print as image" under Advanced is not ticked.

The poster is divided into a grid of tiles, each printed on a normal sheet (A4 or US Letter, or A3 or Tabloid if your printer takes them) with a small overlap between neighbouring tiles. After printing, you trim the overlap off one edge of each inner tile, align the sheets using the printed guides and join them with tape from the back.

Home printers cannot print to the paper edge and cutting is never perfectly straight. The overlap (10 mm by default) duplicates a strip of the artwork on both neighbouring tiles, so small trimming errors disappear inside the joint instead of leaving white gaps.

Build complete rows first, then join the rows to each other. An A0 poster on A4 comes to eighteen sheets at minimum and twenty-one at the default margin and overlap, and if you work outwards from the middle or join sheets as they come off the printer, every small misalignment adds to the next one — by the far corner it is visible. Working a row at a time keeps the error in one direction where you can still correct it. Lay the whole grid out unglued first, using the row and column label in each margin, and check it against the preview above before any tape comes out. Tape from the back, and let the sheet underneath be the one that keeps its overlap.

Short corner ticks show where to cut (the left edge of every column after the first, the top edge of every row after the first). The light dashed line shows where the edge of the next sheet should sit when you glue or tape the overlap. A small label in the margin identifies each tile's row and column.

150 DPI is the large-format standard and the right default: posters are viewed from a distance. Choose 300 DPI only for small posters (A3/A2) that will be inspected up close — file size roughly quadruples. 96 DPI is a quick draft for checking the layout.

Yes, by default. Each sheet is cut from your original PDF page and clipped to its tile, so text, lines and shapes stay vector — sharp at any poster size, at exact scale, and the file stays small. That suits sewing patterns, plans and designs exported from Canva or Illustrator. A rotated PDF page (or one with a custom unit size), and an image such as a JPG or PNG, is tiled as a high-resolution image at the output DPI instead; at 150–300 DPI that is indistinguishable at poster viewing distance.

Open the pattern PDF here and choose "Same size as the PDF page, 100%" as the poster size — the option appears once a PDF is loaded and shows the page’s size. Pick A4 or Letter sheets: the splitter tiles the page 1:1, nothing enlarged or shrunk, with overlaps, cut marks and a check line on the first sheet. Print at 100% ("Actual size"), then measure the pattern’s own test square before cutting fabric. If the designer also publishes a print-at-home A4 or Letter version, that one already has their own assembly marks.

Choose "Custom size…" as the poster size and enter the largest picture the sheets can hold. A home printer leaves a 5 mm margin and every join needs a 10 mm overlap, so four A4 sheets in a 2 × 2 grid make a poster up to 390 × 564 mm (four Letter sheets 402 × 529 mm), not the full A2 that four sheets add up to. For the same reason two A4 sheets make 287 × 390 mm: an A3 picture fits on two only at about 92%, and at full size it takes 4 sheets. A tarpapel for a school project, the paper poster used in the Philippines, prints the same way on short bond (Letter) or A4.

The generated PDF is always at true scale: each page is exactly the paper size you chose, so print it at 100% ("Actual size") with scaling off. If you use the grid numbers with your own PDF reader's poster mode instead, the same rule applies.

10 mm suits most home printers. If your printer has unusually wide unprintable margins (some are 5 mm or more per edge), raise the overlap to 15 mm so alignment stays easy.