The document that prints slightly wrong
It looks right on screen and comes out of the printer with a thin white band down one side, or with the text a few per cent smaller than it should be, or spread over twice as many sheets as expected. Page size in PDFs is a genuinely fiddly subject involving three different rectangles, two paper standards that are close enough to be confusing, and a print dialog that quietly scales things. This guide covers what decides the printed result and which operation fixes each problem.
A4 and Letter are almost the same, which is the problem
| Width | Height | Used in | |
|---|---|---|---|
| A4 | 210 mm / 8.27 in | 297 mm / 11.69 in | Most of the world |
| US Letter | 216 mm / 8.5 in | 279 mm / 11 in | United States, Canada, parts of Latin America |
| Difference | Letter is 6 mm wider | Letter is 18 mm shorter |
Six millimetres and eighteen millimetres are small enough that a document prints without an obvious error and wrong enough to spoil it. An A4 document printed on Letter loses 18 mm from the bottom or gets scaled down to fit, which shifts every margin. A Letter document on A4 leaves an uneven band. If a document crosses borders, Resize PDF Pages converts every page properly rather than leaving the print driver to improvise.
The three rectangles
Each PDF page carries several boxes, and the two that matter in practice are:
- MediaBox — the full sheet. This is the page's real size.
- CropBox — the region a viewer displays. Usually identical to the MediaBox, but not always.
When they differ, the document shows one size on screen and prints another, which is the source of a whole family of confusing bug reports. It also means cropping a PDF typically shrinks the CropBox and leaves the content outside it in the file — hidden, not deleted. That is fine for tidying margins and entirely unsuitable for removing something you do not want seen.
Fitting more on a sheet
Printing several pages per sheet saves paper and makes handouts easier to carry. The trade is legibility, and the maths is unforgiving: two pages per sheet means each is at roughly 71% linear scale, four means 50%, nine means 33%.
| Pages per sheet | Scale of each | 10 pt body text becomes | Usable for |
|---|---|---|---|
| 2 (side by side on landscape) | 71% | About 7 pt | Reading comfortably |
| 4 | 50% | About 5 pt | Reference, slides, skimming |
| 6 | 41% | About 4 pt | Slides with large type only |
| 9 | 33% | About 3 pt | Contact sheets, not reading |
N-Up Pages builds this into the document itself rather than relying on the print dialog, which means the recipient gets the layout you intended and the file can be checked before it is sent. Slide decks with large type survive four-up comfortably; dense reports do not survive two-up.
Margins, bleed and the unprintable edge
Almost every desktop printer has a non-printable margin of three to five millimetres it physically cannot reach. A PDF designed to the very edge of the page will either lose that strip or be scaled down to fit, and scaling is what introduces the mysterious few per cent size change people notice in body text.
- Set the print dialog to 100% or Actual Size whenever exact scale matters.
Fit to pageis the default in many viewers and is the usual culprit. - Keep content 10 mm from the edge when designing anything that will be printed on an office printer.
- Trim excess margins with Crop PDF when a scan has wide white borders — the content then prints larger at the same paper size.
- For professional printing, the shop will ask for bleed and crop marks, which is a different specification from anything an office printer needs. Ask them before exporting rather than after.
Scans and books
Two scanning artefacts have specific fixes. A book or magazine scanned with two pages on each sheet should be cut down the middle rather than cropped twice — Halve PDF Pages splits every sheet into two properly numbered pages. And a duplex scan whose reverse sides came out inverted needs rotation rather than re-scanning: Rotate PDF turns pages losslessly, changing a flag rather than re-rendering the image, so nothing is degraded.
Either way, do the structural work before compressing. Compression re-renders pages, and re-rendering a page you are about to cut in half wastes the quality you paid for.