How to Resize PDF Pages (Change A4 to Letter and Back)

To resize PDF pages, open the file in an online editor, choose the target page size (for example A4 or US Letter), and pick how the content should fit: scaled to the new size or kept at its original scale. Apply it to all pages or selected ones, then download. A4 to Letter is the most common switch, and it takes under a minute.

Key takeaways

• Resizing changes the page dimensions (the physical size of the sheet), which is different from compressing the file or cropping the margins.
• A4 and US Letter are close but not identical, so a clean switch needs you to decide whether content scales to fit or stays at its current size.
• The cleanest method is an online editor where you set the target size and a fit option, then apply it to every page or just the ones you choose.
• The classic failure is stretched or cropped content, which happens when the tool forces a fit instead of scaling proportionally.
• Scanned PDFs resize fine as images, but the text inside them still won't be selectable afterward.
• Print settings can resize on the fly without changing the file, which is sometimes all you actually need.

What "resize a PDF page" actually means

There are three things people lump under "resize," and sorting them out saves a lot of frustration.

The first is changing the page dimensions: turning an A4 page into a Letter page, or making every page a fixed size. That is what this guide covers. The second is making the file smaller in megabytes, which is compression, not resizing. The third is changing the visible area by trimming margins, which is cropping. They sound similar but do completely different jobs, and a tool built for one won't do the others.

When you genuinely want to change how big the content looks rather than the sheet itself, that's scaling, and we cover it in detail in making a PDF page bigger or smaller by scaling its dimensions. If you only need to swap the orientation, see changing a PDF from portrait to landscape. This article is specifically about the sheet size, with A4 to Letter as the headline case.

A4 vs Letter: the numbers that matter

A4 and US Letter are the two standards almost everyone runs into. They're similar enough that a document made for one usually looks fine on the other, but different enough to cause clipped headers or a thin white strip at the bottom if you ignore it.

The takeaway: Letter is slightly wider than A4 (216 mm vs 210) but noticeably shorter (279 mm vs 297). So going A4 to Letter, the content gains a touch of side room but loses about 18 mm of height. That lost height is exactly where the bottom of an A4 page can get cut off if you don't scale it. Going the other way, Letter to A4, you gain height but the page is a hair narrower, which can clip wide content on the right edge.

How do I change the page size of a PDF?

Here's the reliable path with an online editor. You upload, set the target size and a fit option, and download.

1. Open your PDF in the editor. Go to the PDF editor and upload the file you want to resize. It opens in your browser, no install needed.
2. Open the page size controls. Look for a page setup, resize, or page size option. This is where you choose the new dimensions.
3. Pick the target size. Choose A4, US Letter, or a custom size by entering width and height. If you're switching A4 to Letter, select Letter here.
4. Choose how the content fits. This is the important choice. Pick "scale to fit" (or "fit to new size") to shrink or grow the content proportionally so nothing is lost, or "keep original size" to leave the content untouched and simply change the sheet around it.
5. Decide the scope. Apply the new size to the whole document or only selected pages. Mixed-size files are common, so most editors let you target specific pages.
6. Preview before you commit. Check a page or two, paying attention to the top header and bottom margin where clipping shows up first.
7. Save and download. Export the file. The new page size travels with the PDF wherever it goes.

That covers the standard switch. The fit option in step 4 is where most resizing goes right or wrong, so it's worth understanding properly.

Scale to fit vs keep original size

These two options produce very different results, and choosing the wrong one is the single most common resizing mistake.

Scale to fit resizes your content proportionally to match the new page. Going A4 to Letter, your text and images shrink very slightly so the whole page fits inside the shorter Letter height. Nothing gets cut off, and the proportions stay correct. The trade-off is that everything is now a touch smaller, though the change is tiny between A4 and Letter and usually invisible to the eye.

Keep original size changes the sheet dimensions but leaves the content exactly as it was. This is fine when the content sits comfortably within the smaller of the two sizes, but if your A4 page used the full height, the bottom will be clipped on a shorter Letter sheet.

As a rule of thumb: if you're going to a shorter or narrower page, choose scale to fit. If you're going to a taller or wider one, keep original size is usually safe.

The catch: stretched, cropped, or off-center content

Here's what nobody warns you about. A poorly built resize tool will stretch content to fill the new page, distorting circles into ovals and making text look subtly wrong. A clean tool only ever scales proportionally, the same factor horizontally and vertically, so shapes stay true. If your output looks squashed or pulled, the tool forced a non-proportional fit, and you should redo it with a proportional option.

The second trap is cropping. Choosing "keep original size" when moving to a smaller sheet doesn't shrink anything, it just hides whatever falls outside the new boundary. The page looks fine in a thumbnail but the bottom line of text is gone. Always check the edges of a full page, not just a thumbnail.

The third is centering. When content is smaller than the new page, where does it sit? A good tool centers it; a careless one pins it to a corner, leaving lopsided margins. The preview is your friend here, so use it before downloading.

Platform variations

You don't always need an online editor. The right tool depends on what you have and how permanent you want the change.

• Online (any device): The most flexible route. You get an explicit target size, a fit option, and per-page control, and it works the same on Windows, Mac, a Chromebook, or a phone. Best when you want the resize baked into the file.
• Windows: You can "print" to the Microsoft Print to PDF driver and choose paper size in the print dialog. It re-renders the document at the new size, which flattens some interactive elements but is quick for a one-off.
• Mac: Preview can resize via the print dialog (File > Print, then the paper size dropdown, then "Save as PDF"). It's handy but gives you less control over the fit than a dedicated editor.
• iPhone and Android: Mobile PDF apps vary widely; many only offer paper size at the print stage. For real per-page resizing on a phone, an online editor in the browser is usually the most capable option.

A note on the print-dialog approach: it resizes the output, not the stored page geometry, and it often rasterizes or flattens the document. That's fine for printing or sending a snapshot, but if you need the file itself to genuinely be Letter size with its text intact, an editor that changes the page boxes is the better call.

Resizing scanned PDFs

A scanned PDF is a stack of images, so resizing it is really resizing pictures. Switching A4 to Letter works, but two things are worth knowing.

First, the text in a scan isn't real text, it's part of the image, so it stays unselectable after resizing. Resizing won't make it searchable; that needs OCR, which is a separate step.

Second, scaling a scan up to a larger page can look soft, because you're enlarging fixed pixels. Scaling down (the usual direction for A4 to Letter, since you're losing height) is safe and often looks a touch crisper. If you must enlarge a scan significantly, expect some loss of sharpness, and don't push it further than the original resolution comfortably allows.

When you don't need to resize the file at all

Sometimes the simplest fix is to leave the file alone. If your only goal is to print an A4 document on Letter paper, your printer's dialog can do that with a "fit to page" or "scale to fit" checkbox, no editing required. The stored file stays A4; only the printout changes.

This is the better call when the resize is a one-time thing, like printing a document a colleague sent you. Editing the page size only makes sense when the file itself needs to be a specific size, for instance because a portal, a print shop, or a template demands Letter, or because you're combining pages from different sources into one consistent document.

A quick word on privacy, since you're uploading a document. An online editor processes your file on a server to make these changes, and files aren't kept long-term. That's normal for browser-based editing, but it's worth knowing before you upload anything sensitive.

FAQ

How do I change the page size of a PDF?

Open the PDF in an online editor, find the page size or page setup control, and choose your target size such as A4 or US Letter. Then pick a fit option: "scale to fit" shrinks or grows the content proportionally so nothing is lost, while "keep original size" changes only the sheet. Apply it to all pages or selected ones, preview the result, and download.

What's the difference between A4 and Letter?

A4 measures 210 x 297 mm (8.27 x 11.69 in), and US Letter measures 216 x 279 mm (8.5 x 11 in). Letter is slightly wider but noticeably shorter, by about 18 mm. That height difference is why an A4 page can lose its bottom margin when forced onto Letter without scaling. A4 is the worldwide ISO standard; Letter is standard in the US and Canada.

Will resizing my PDF lower its quality?

Resizing real (vector) text and graphics keeps them crisp at any size, because they're drawn from instructions, not pixels. Scanned or image-based PDFs are different: scaling them up enlarges fixed pixels and can look soft, while scaling down usually stays sharp. As long as your tool scales proportionally rather than stretching, vector content won't degrade.

How do I resize a PDF to fit Letter paper without cutting anything off?

Choose the "scale to fit" (or "fit to new size") option rather than "keep original size." Because Letter is shorter than A4, keeping the original size can clip the bottom, but scaling fits the whole page inside the new boundary proportionally. Then preview a full page, checking the top and bottom edges, before you download to confirm nothing was lost.

Can I resize just one page in a PDF instead of the whole document?

Yes. A good online editor lets you apply a new page size to selected pages rather than the entire file, which is essential for mixed-size documents, like an A4 report with a Letter-size cover. Select the pages you want, set the target size and fit option, and leave the rest untouched. Always preview the changed pages afterward.