How to print a formboard at 1:1 (and check that you did)

Why boards print short

A formboard PDF is drawn edge to edge at true size. When the print dialog is set to “Fit”, the printer shrinks the page into its printable area. With 4.2 mm margins on A4 that factor is min(201.6/210, 288.6/297) = 0.96. Nothing on the page looks wrong — the lines are just 4 % shorter. Some print dialogs also remember the last choice, so a board printed correctly yesterday can print short today.

Settings that work

• Acrobat or Acrobat Reader: Page Sizing → “Actual size”.
• Chrome's PDF viewer: Scale → “Actual size” or 100 %. Chrome passes the PDF's “don't scale” preference to its print dialog.
• Firefox's built-in viewer: use another viewer. It does not honour the PDF's no-scaling preference (Mozilla bug 1243580) and has a long-open bug about shrinking printed output (bug 847049).
• macOS Preview: Scale 100 %.
• In every case, switch off “Fit to page”, “Shrink oversized pages” and any “Print to fit” in the printer driver.

Check before you build

1. Print the one-page calibration sheet first, with a 100 mm square and rulers.
2. Measure the square both ways with a steel rule. 100 mm is right; 96 mm means the page was fitted.
3. If a printer is consistently off by a small amount even at 100 %, note the factor in X and Y and save it as that printer's correction.
4. On every tile, measure the 100 mm ruler again before taping the tiles together.

Tiles: putting the board together

• Tiles overlap; the registration crosses in the overlap appear on both neighbouring tiles. Lay one over the other until the crosses match.
• Work from the board datum (lower left). Peg positions carry X/Y coordinates from it, so you can mark the board out with a tape measure if a tile is missing.
• Empty tiles are not printed; the tile numbers stay the same, and the mini-map on each tile shows which ones were skipped.

Plotters and long boards

A roll plotter prints the board in one piece. HP specifies line accuracy of ±0.1 % for its DesignJets under controlled conditions — about ±1 mm per metre. The PDF standard recommends a maximum page size of 200 inches (5,080 mm), so a longer board should print as strips.

In Zorowire

Every formboard PDF asks viewers not to scale, keeps content inside a safe margin, and puts a 100 mm check ruler and the instruction to print at 100 % on each page. You can print tiled A4, A3, Letter or Tabloid with overlap and registration marks, or one piece up to 5,080 mm, and save a scale correction per printer.