Excel exports the PDF at the wrong page size (A4 vs Letter)

Short answer: Excel has an option that quietly converts between A4 and Letter for you. It lives in File → Options → Advanced → General, and it is called “Scale content for A4 or 8.5x11 inch paper sizes.” When it is on, Excel rewrites the paper size to match your Windows regional setting, so a sheet you set to A4 exports as Letter and every margin shifts. Turn that option off, then set the size deliberately in Page Layout → Size, and re-check the margins before exporting.

The full fix, in order

1. File → Options → Advanced. Scroll to the General section and clear “Scale content for A4 or 8.5x11 inch paper sizes.” This is per-user, not per-file, so it has to be done on the machine doing the export.
2. Page Layout → Size. Choose A4 or Letter explicitly. Do not rely on the default — the default comes from the printer driver.
3. Check the printer. Excel takes the available paper sizes from the currently selected printer. If that printer only offers Letter, A4 will not stay set. Switch the default printer to one that offers the size you want, including Microsoft Print to PDF.
4. Page Layout → Margins → Custom Margins. A4 is taller and narrower than Letter, so a layout tuned for one always needs its margins re-checked on the other.
5. Export and confirm. Open the PDF’s document properties and check the page dimensions. A4 is 210 × 297 mm; Letter is 8.5 × 11 inches.

Why it matters more than it sounds

Paper size is not cosmetic when the sheet is wide. Letter is about 6 mm narrower than A4, and on a table that was already close to the edge, those few millimetres are the difference between the last column landing on the page and landing on a separate strip of pages at the back. Half the “Excel cut off my columns” reports that arrive from a colleague’s machine are really this: the file is fine, the paper size changed under it.

The same applies in reverse across regions. A workbook built in a Letter region and exported in an A4 region repaginates, which is why the PDF a colleague sends you can have different page breaks from the one you produce from the identical file.

If you want the paper size to stop mattering

The deeper fix is a renderer that decides the layout from the sheet rather than from the page setup: measuring the real column widths, choosing orientation per sheet, keeping every row whole, and slicing a too-wide table across pages with the label column repeated. Then a paper-size change moves the text around rather than losing a column off the edge. CrazySmartPDF’s free web tool does that in a browser for a single file — it uploads, converts and deletes the file — and the Windows apps do it offline. See how it works.

FAQ

Why does Excel keep changing my page size to Letter? The “scale content for A4 or 8.5x11 inch paper sizes” option in File → Options → Advanced converts between the two based on your regional settings. Clearing it stops the substitution.

Why can I not select A4 in Page Layout → Size? The size list comes from the selected printer. If that printer does not offer A4, Excel cannot either. Change the default printer, then set the size.

The PDF is the right size but the margins moved. Why? A4 and Letter have different proportions, so a margin set that fitted one leaves different room on the other. Re-set custom margins after changing paper size.

Does the page size affect where my page breaks fall? Yes. Excel paginates against the usable area of the paper, so a size change moves every break — which is why the same file can produce different PDFs on two machines.