Transcript and chapter notes
0:00 · The whole PDF page
A PDF can have several page boxes. This example has a 216 by 303 mm whole page.
Its MediaBox and CropBox are identical. The visible page includes the bleed.
0:10 · Trim and 3 mm bleed
The finished A4 TrimBox is 210 by 297 mm, inset 3 mm from every edge.
Add both edges: 210 plus 3 plus 3 is 216. 297 plus 3 plus 3 is 303.
0:22 · Why Fit becomes 97.22%
Fit this whole page onto a full A4 sheet: the limiting ratio is 210 divided by 216, or 97.22 percent.
The A4 trim then shrinks to 204.17 by 288.75 mm. A printer's usable area may make it smaller still.
0:38 · Actual size and a measured proof
Actual size, or 100 percent, preserves the original 210 by 297 mm trim.
Use stock that can hold the page. Measure a 100 mm gauge. These are authored dimensions, not a printer test.
The two portrait fit ratios are 210 ÷ 216 ≈ 0.972222 and 297 ÷ 303 ≈ 0.980198. Taking the smaller ratio keeps the whole outer page within a full A4 sheet. Printer margins and application behaviour are separate from this ideal calculation.
Repeat the example
- Download the original A4 bleed specimen.
- Open it in the PDF page-box checker. The MediaBox is 216 × 303 mm; TrimBox is 210 × 297 mm.
- Compare fitting MediaBox and TrimBox to A4. Then check the print application’s own preview.
- For a physical proof, use the 100 mm calibration gauge and measure the printed line.
Read the full page-box explanation, formulas and sources. Download the English captions.