The five rectangles inside a PDF

Your page has five sizes, not one

A PDF page carries up to five rectangles, and most disagreements with a printer are one of them being missing or wrong.

• MediaBox: the sheet the page is described on. Always present. Everything else is defined inside it.
• CropBox: what a viewer displays. Defaults to the MediaBox.
• BleedBox: the area including bleed, where artwork may extend.
• TrimBox: the finished size after cutting. This is the one that matters.
• ArtBox: the meaningful content area. Rarely used in commercial print.

The press positions and cuts from the TrimBox. A file with no TrimBox forces the operator to guess, and “no trim box defined” is one of the most common preflight rejections there is.

A worked example

A 90 × 54 mm visiting card with 3 mm bleed and crop marks:

• TrimBox: 90 × 54 mm. The card.
• BleedBox: 96 × 60 mm. Trim plus 3 mm on each side.
• MediaBox: larger again, typically 106 × 70 mm or so, to make room for crop marks and any colour bars outside the bleed.

A very common error is exporting the page at 96 × 60 mm with no boxes defined. The printer then sees a 96 × 60 mm page and either cuts to it (producing an oversized card with no bleed) or asks you to re-export.

Reading them

pdfinfo -box job.pdf

Output looks like:

Page size:      300.47 x 198.43 pts
MediaBox:       0.00  0.00  300.47 198.43
CropBox:        0.00  0.00  300.47 198.43
BleedBox:       8.50  8.50  291.97 189.93
TrimBox:       17.01 17.01  283.46 181.42
ArtBox:        17.01 17.01  283.46 181.42

Check the arithmetic. TrimBox width here is 283.46 − 17.01 = 266.45 pt = 93.99 mm. BleedBox width is 291.97 − 8.50 = 283.47 pt = 100 mm. So trim is 94 mm and bleed extends 3 mm each side. If those numbers are not the sizes you agreed, stop before sending.

mutool info and Acrobat’s Document Properties give you the same information.

Acrobat also draws the boxes on screen: Preferences ▸ Page Display ▸ Show art, trim & bleed boxes. Turn it on once and every PDF you open shows you its geometry without a command line.

Setting them correctly

The boxes come from how you set up the document and the export, not from a separate dialog.

• Set the document page size to trim, not to trim-plus-bleed. This is the single mistake that generates most of the box problems.
• Set bleed in the document setup (3 mm all round), not by drawing a larger rectangle.
• On export, tick use document bleed settings and turn on crop marks with an offset of at least the bleed amount, so the marks sit outside the bleed rather than printing into it.

Scribus, InDesign, Affinity and CorelDRAW all follow this pattern. In Inkscape, which has no native bleed concept, set the SVG page to the trim size and use the PDF export’s bleed/margin field, or, better, do the final assembly in Scribus.

Fixing a file you cannot re-export

Occasionally you receive a PDF with wrong boxes and no source. Ghostscript can rewrite them:

gs -o fixed.pdf -sDEVICE=pdfwrite \
   -dUseTrimBox=true -dFIXEDMEDIA \
   -c "[/CropBox [17 17 283 181] /PAGES pdfmark" -f job.pdf

pdftk, qpdf and mutool can also manipulate page geometry. Treat all of it as a rescue, not a workflow: the right answer is to fix the source document and export again.

Crop marks, registration marks and colour bars

• Crop marks show where to cut. Offset them beyond the bleed.
• Registration marks are printed in all plates and let the press check alignment. The press adds these; you normally do not.
• Colour bars are strips of known patches the press measures during the run. Also theirs, not yours.
• Page information (filename, date, plate name) is optional and useful on a multi-page job.

Do not draw any of these by hand. Every application generates them, aligned to the boxes, and a hand-drawn crop mark in the wrong place is worse than none.