The two sizes
| Size | Millimetres | Inches | Points (PDF units) | Where |
|---|---|---|---|---|
| A4 | 210 × 297 | 8.27 × 11.69 | 595 × 842 | Almost everywhere |
| US Letter | 216 × 279 | 8.5 × 11 | 612 × 792 | United States, Canada, parts of Latin America |
| Legal | 216 × 356 | 8.5 × 14 | 612 × 1008 | US legal documents |
Letter is a little wider and noticeably shorter. Content designed for one and printed on the other is either clipped at the bottom, or scaled down by a few percent with uneven margins — which is why a form that “must print at 100%” fails, and why a print shop rejects a file with mixed sizes.
How PDFs end up mixed
Every source brings its own size. Word uses the locale of whoever created the document. Scanners produce the sheet size on the glass. Slide decks are 16:9 pages. Email attachments from abroad are the other standard. Merging keeps each page’s size, so a bundle assembled from several sources almost always mixes them. Viewers hide the problem by fitting each page to the window; the printer does not.
How to check
Open the file in any viewer and read the page size in its properties, or simply look at the thumbnails in Organize: mixed sizes show as different thumbnail shapes. A print shop’s preflight — or Bindery’s PDF/X preflight — lists page-size inconsistencies explicitly.
Making every page the same size
Resize rebuilds every page at A4, Letter or Legal, portrait or landscape, with the original content scaled proportionally and centred. Nothing is cropped; a wide page on portrait A4 gets margins above and below. The page is embedded as a drawing and scaled, so text stays selectable and lines stay sharp — it is not a re-render. Choose a percentage instead to scale the whole document, useful for oversized drawings. Fields and bookmarks do not carry into the rebuilt document; flatten a filled form first.
When you want to change the visible area instead
Trimming scanner borders or a slide footer is a different job: Crop sets a crop box that tells viewers what to show and keeps the sheet size. For two or four pages per sheet, or a folded booklet, Booklet & N-up places pages on A4 or Letter sheets. For a print shop, ask for their spec — size, bleed, PDF/X version — and prepare the file with PDF/X for print.
Forms that must print at exact scale
Government and legal forms are sometimes read by machines or measured by hand, and they say “print at 100%, do not scale”. For those, do not resize the content; print on the paper the form was designed for, or set the page size in Resize to match the form and let the small margin difference show. If the original form is Letter and your printer has A4, a 100% print clips 18 mm at the bottom — check that nothing important is there before you rely on it.
Quick reference
- Sending to Europe, Asia, Africa, Australia, Latin America: A4.
- Sending to the United States or Canada: Letter; Legal only when the recipient says so.
- Mixed bundle, unknown printer: pick one size and resize the whole file; most viewers scale to fit anyway, and a uniform file prints predictably.
- Slides and drawings: keep their own size for screen use; resize to A4 or Letter landscape only for printing.
- Scans: they are already the size of the paper that was scanned; resize only if the destination insists.
Every tool linked here rewrites a new file and leaves the original untouched on your device, so trying a size costs nothing.