What “page size” actually is
Every PDF page carries its own dimensions, stored in the file independent of any printer. When you open a PDF, the viewer scales it to your window; that scaling is an illusion. Print it, and the real dimensions take over. A page sized A4 (210 × 297 mm) printed on Letter paper (215.9 × 279.4 mm) will not fit without scaling, and the two are not interchangeable even though they look similar at a glance.
Orientation is separate from size: portrait is taller than it is wide, landscape is wider than tall, and the physical dimensions simply swap. A document can mix orientations page by page, which is legal and sometimes exactly what you want — and occasionally exactly what you did not want.
Common page sizes
- **A4 — 210 × 297 mm (8.27 × 11.69 in).** The default across most of the world.
- **Letter — 215.9 × 279.4 mm (8.5 × 11 in).** The default in the US and Canada; slightly wider and shorter than A4.
- **Legal — 215.9 × 355.6 mm (8.5 × 14 in).** Used for longer contracts.
- **A3, A5, and photo sizes** — used for posters, booklets and photo sheets. The full supported list lives on the formats and standards reference.
Changing page size safely
- Open Document Print Prep and load the PDF.
- Choose the target paper and orientation, and how content should fit — fit keeps everything inside the new page, which is the safe choice.
- Generate and inspect: check that no text was clipped at the edges, that nothing was scaled to illegibility, and that every page came out the same size.
- For a document that will be printed with several source pages per sheet, use Multiple Pages per Sheet instead — it re-imposes without rasterising, so text stays sharp.
Fit cannot create detail. Shrinking a large page onto A4 makes the text physically smaller, which may still be readable but will not be at the original apparent size. Check a printed sample when legibility matters.
When pages come out the wrong size
- **Mixed sizes in one file** — often the result of merging PDFs from different sources. Re-paginate to one paper size.
- **Content clipped at the edges** — the original page was larger than the target, or margins were zero. Use fit rather than an exact scale, or increase the margin.
- **A blank border all round** — the source page was smaller than the target. That is normal and usually harmless; if it matters, choose a smaller paper.
- **Everything rotated 90°** — individual pages carry their own rotation. Fix them in Rotate PDF pages first, then resize.
Common questions
Is A4 the same as Letter?
No. A4 is taller and narrower; Letter is wider and shorter. Files prepared for one can look wrong or be clipped when printed on the other.
Can one PDF contain several page sizes?
Yes. Each page stores its own dimensions, so a merged file can mix them. If that causes problems at print time, re-paginate everything to a single paper size.
Does changing page size change how sharp the content is?
Not by itself. Vector text stays sharp at any size; embedded images only lose apparent sharpness when scaled up beyond the pixels they actually contain.