Field guide
Print a poster across A4 sheets
The Print mode on the front page does this job: choose the sheet, how many across and down, the printer margin and the overlap, and it writes one file per sheet with trim marks and glue lines in the margin. What follows is the arithmetic behind it. Poster tiling divides one pixel canvas into physical sheets, and printer margins and the overlap used for joining determine whether the assembled image keeps its intended dimensions.
01
The archive now carries a print-ready PDF: a cover page with the finished size and the instruction to print at 100 % / actual size, then one page per sheet at the paper's exact size with the picture placed in millimetres and the trim marks drawn as vectors. At a print shop, hand over the PDF and ask for actual size with no fit-to-page. An assembly-map picture in the same ZIP shows where every numbered sheet goes.
02
Choose final poster size first, then calculate rows and columns from the printable area rather than the full 210 by 297 millimetre sheet.
03
Add a small overlap so one page can be trimmed and aligned over its neighbour. Butt-joining two unprinted margins creates a visible white seam.
04
Place crop or registration marks outside important image content. Marks inside the picture are difficult to remove cleanly after assembly.
05
Print at actual size with scaling disabled and verify one ruler test page. Automatic fit-to-page silently changes every tile and prevents accurate alignment.
