Choose A3 as the paper size, then pick Actual size for an A3 file or Fit for anything smaller. An A4 page enlarges to exactly 141.4% and fills the sheet, while a Letter page stops at 137.6% and leaves a blank band. Here's where the settings live and what scaling does to your text.
Check first, because the fix depends on the answer. Open the document properties (Ctrl+D in Acrobat, Tools > Show Inspector in Preview) and read the page size. Page sizes are stored in points, 72 to the inch, so viewers may show either unit:
| Paper | Millimeters | Inches | PDF points |
|---|---|---|---|
| A4 | 210 × 297 mm | 8.27 × 11.69 in | 595 × 842 |
| A3 | 297 × 420 mm | 11.69 × 16.54 in | 842 × 1191 |
| 11 × 17 (Tabloid) | 279.4 × 431.8 mm | 11 × 17 in | 792 × 1224 |
| A2 | 420 × 594 mm | 16.54 × 23.39 in | 1191 × 1684 |
A3 is exactly twice the area of A4. That's the whole logic of the A series: fold a sheet in half across its long side and you get the next size down, with the same shape. It's why A sizes scale so cleanly into each other and why US sizes don't.
Here's where the setting usually lives. This list comes from each app's menus, not from a printing test on every version, so labels may differ:
| App | Where to choose A3 | Scaling |
|---|---|---|
| Adobe Acrobat Reader | Print > Page Setup > Size: A3 | Page Sizing: Actual size, or Fit |
| Chrome, Edge | Print > More settings > Paper size: A3 | Scale: Default or Fit to paper |
| Firefox | Print > More settings > Paper size: A3 | Scale: Fit to page or 100% |
| macOS Preview | Print > Paper Size: A3 | Scale to Fit, or Scale 100% |
| Windows printer driver | Printing Preferences > Paper: A3 | Match the tray and media type |
| Linux (CUPS) | lp -o media=A3 file.pdf | Add -o fit-to-page to scale |
If A3 isn't listed, your driver doesn't offer it, and no PDF app can add it. Most home printers stop at A4 or Legal. Office copiers and wide-format inkjets usually handle it. Otherwise, a print shop will run it from a single PDF.
Fit scales until the page hits the first edge of the paper. We computed these for every pair and placed test pages with PyMuPDF to confirm the two most common: 12 pt type measured 16.97 pt for A4 on A3 and 7.98 pt for A3 on Letter.
| PDF page | Paper | Fit scale | 12 pt becomes | Printed size | Blank left over |
|---|---|---|---|---|---|
| A4 | A3 | 141.4% | 17.0 pt | 297 × 420 mm | 0 × 0 mm |
| Letter | A3 | 137.6% | 16.5 pt | 297 × 384 mm | 0 × 36 mm |
| Legal | A3 | 118.1% | 14.2 pt | 255 × 420 mm | 42 × 0 mm |
| 11 × 17 | A3 | 97.3% | 11.7 pt | 272 × 420 mm | 25 × 0 mm |
| A2 | A3 | 70.7% | 8.5 pt | 297 × 420 mm | 0 × 0 mm |
| A3 | A4 | 70.7% | 8.5 pt | 210 × 297 mm | 0 × 0 mm |
| A3 | Letter | 66.5% | 8.0 pt | 198 × 279 mm | 18 × 0 mm |
| A3 | 11 × 17 | 94.1% | 11.3 pt | 279 × 395 mm | 0 × 37 mm |
Those figures ignore printer margins. A printer that can't reach within 5 mm of the edge prints a true A3 page at 96.6% on Fit, and A4 on A3 falls to 136.7%. If an exact scale matters, as it does for a drawing, set 100% and accept the clipped edge, or use a printer rated for borderless output, and then measure a known dimension on the sheet.
Text and vector graphics won't. They're stored as shapes and redraw sharply at any size. Scanned pages and photos are made of pixels, so enlarging spreads them out by the same 141.4%:
| Image resolution at A4 | Resolution on A3 | What to expect |
|---|---|---|
| 400 ppi | 283 ppi | Sharp |
| 300 ppi | 212 ppi | Sharp |
| 200 ppi | 141 ppi | Fine for posters viewed from a step away |
| 150 ppi | 106 ppi | Soft up close |
The "what to expect" notes are a rule of thumb rather than a measurement, and viewing distance changes how much it matters. A scanned form at 150 ppi will look soft. If that's what you've got, rescan it if you can.
Letter is a different shape: 1.29 times as tall as it is wide, against 1.41 for A3. Fit stops at the width, so Letter on A3 leaves about 36 mm blank across the page. Legal goes the other way and leaves 42 mm at the sides. To fill the sheet you'd have to cut something off, and our PDF crop tool lets you choose what goes.
A3 and 11 × 17 trip people up because they look alike but aren't. A3 is wider and shorter, so you lose a little either way. If a US print shop only stocks Tabloid, A3 fits at 94.1%, or have them trim. Our 11 × 17 guide covers that size in more depth.
Yes, in three ways, and only the first keeps it all on one sheet:
The reverse trick is handy too. Two A4 pages fit side by side on landscape A3 at exactly 100%, so "2 pages per sheet" gives you a true-size spread, which is the basis of booklet printing. Two Letter pages come out at 97.3%.
If pages print sideways, the file's rotation may be wrong rather than your settings. Rotate PDF fixes it permanently. And if one file has a mix of sizes, this guide explains why and what to do about it.
Set the paper size to A3 in the print dialog and choose Fit. A4 enlarges to 141.4% and fills the whole sheet because the two sizes have the same shape, so 12 pt text becomes 17 pt. Printer margins may bring that down to about 137%.
Your printer driver doesn't offer it, usually because the printer can't feed paper that large. PDF apps only list the sizes the driver reports. Check that the right printer is selected, since a copier and a home inkjet on the same network list different sizes.
Neither is simply bigger. A3 is 297 by 420 mm and 11 by 17 is 279.4 by 431.8 mm, so A3 is 17.6 mm wider and 11.8 mm shorter. A3 printed on 11 by 17 scales to 94.1%, and 11 by 17 printed on A3 scales to 97.3%.
70.7%, or just choose Fit. A3 and A4 have the same shape, so it fills the page apart from the printer margins. Text at 12 pt becomes about 8.5 pt, so check small labels on a test page.
Two, side by side on a landscape A3 sheet, at exactly 100%. A3 is 420 mm long and each A4 page is 210 mm wide. Some printer margin still applies, so anything right at the edge of a page may be clipped.