How to Crop a PDF on Mac, Windows and Online

Cropping a PDF means trimming the visible edges of a page — cutting off a scanner's black border, killing the white margins so the text fills a tablet screen, or lopping a header off every page. On a Mac you can do it in Preview, which is already installed, in about thirty seconds. On Windows there is no built-in way, so you need a browser-based tool or Acrobat.

Before you crop anything, there is one fact worth ninety seconds of your time, because it surprises almost everyone and it has bitten people badly. Cropping a PDF does not delete the part you cropped away. It hides it behind a smaller viewing window, and the original content stays in the file where anyone can get it back. We tested this rather than assuming it: we cropped a page down to roughly 18% of its original area, and the file went from 1,251,282 bytes to 1,250,884 — a change of -0.0%. The photo we had cropped out was still sitting in the file, in full.

So this guide covers both halves: how to crop on every platform, and what to do instead when you need the cropped part genuinely gone.

Every PDF page carries several rectangles that describe its geometry. Two of them matter here:

• MediaBox — the real, physical size of the page. For US Letter this is 612 × 792 points (72 points to the inch).
• CropBox — the region a viewer or printer is told to display. By default it matches the MediaBox exactly.

When you crop a PDF, essentially every tool — Preview, Acrobat, and the online ones — does the same thing: it shrinks the CropBox and leaves the MediaBox alone. The page content is untouched. You have changed the window, not what is behind it.

We ran this on a test file and read the boxes before and after:

BEFORE   MediaBox: [0, 0, 612, 792]   CropBox: [0, 0, 612, 792]
AFTER    MediaBox: [0, 0, 612, 792]   CropBox: [0, 120, 612, 792]

The MediaBox never moved. Only the CropBox changed, lifting the bottom edge by 120 points and hiding the footer. That single design decision explains every surprising thing about PDF cropping — why the file does not get smaller, why the content comes back, and why a crop can be undone by someone who has never met you.

macOS ships with Preview, and Preview crops PDFs natively. Nothing to install, nothing to upload.

1. Open the PDF in Preview (double-click it; Preview is the default PDF app unless you changed it).
2. If the markup toolbar is not showing, click the Show Markup Toolbar button — the pen-tip icon near the top right — or press Shift + Command + A.
3. Click the selection tool at the left of the markup toolbar and make sure it is set to Rectangular Selection.
4. Drag a rectangle over the area you want to keep. Everything outside it is what gets hidden.
5. Choose Tools → Crop from the menu bar, or press Command + K.
6. Press Command + S to save.

The multi-page catch. If you do nothing else, Preview crops only the page you are looking at. To crop every page the same way, open the sidebar with View → Thumbnails, click the first thumbnail, then press Command + A to select all pages before you drag your rectangle and hit Command + K. Miss this step and you will save a document where page 1 is cropped and pages 2 to 40 are not.

Work on a copy. Preview saves over the original by default, and because a crop is reversible in principle but fiddly in practice, use File → Duplicate (Shift + Command + S) first.

This is the honest answer: Windows has no built-in PDF cropping. Edge opens PDFs and Windows 11 can annotate them, but neither can change page geometry. You have three realistic routes.

1. A browser-based cropper. The fastest option, and if the tool processes files in the browser rather than on a server, your document never leaves your machine. This is the route we would take for a one-off.
2. Adobe Acrobat Pro. Proper crop controls with numeric margins — see the next section. It is a paid subscription, and the free Acrobat Reader cannot crop.
3. Print to PDF with scaling. Open the PDF, press Ctrl + P, choose Microsoft Print to PDF, and set the page size or scaling. This is a blunt instrument — it scales rather than trims, so it will not remove a scanner border cleanly — but it costs nothing and it is already on your PC.

A word on uploads. Most free online croppers upload your PDF to a server, process it there, and promise to delete it later. If the document is a contract, a medical record or anything with a client's name on it, that promise is the entire security model. Prefer a tool that states it runs client-side, and check that the page keeps working if you switch your Wi-Fi off mid-session — that is the quickest way to tell whether the work is actually happening on your machine.

Acrobat Pro gives you the most precise control, including numeric margins and an automatic margin detector. Acrobat Reader, the free one, does not include this.

1. Open the PDF and go to Tools → Edit PDF.
2. Click Crop Pages in the toolbar.
3. Drag a rectangle over the area to keep, then double-click inside it to open the Set Page Boxes dialog.
4. Fine-tune the Top, Bottom, Left and Right margins numerically, or tick Remove White Margins to have Acrobat find the content edges for you.
5. Under Page Range, choose All to apply the same crop to the whole document.
6. Click OK, then save.

Remove White Margins is the one to know about. On a scanned document where every page sits slightly differently on the glass, it beats dragging a rectangle by hand, because it finds each page's own content edge instead of applying one rectangle to pages that do not match.

Acrobat's dialog also exposes the CropBox directly — you will see a Change Page Size section and a box-type selector. That is the same CropBox described above, which is a useful confirmation that the expensive tool and the free ones are doing the identical thing under the hood.

The single most common complaint about PDF cropping is a document where only the first page came out right. Each tool hides the "all pages" control somewhere different:

When one rectangle will not fit every page. Scanned documents drift: page 3 sits 4mm lower than page 2, and a crop tight enough for one clips the other. Two ways out. Either crop loosely, giving yourself a few millimetres of slack on every edge, or use an automatic margin detector that measures each page separately. If the document mixes portrait and landscape pages, crop them in two passes — a single rectangle across both orientations will always butcher one of them.

This is the section that matters. Both of these claims are things we measured today rather than repeated.

The cropped-away content is still there

We built a one-page PDF with the string CONFIDENTIAL-FOOTER-12345 in the bottom margin, cropped the bottom 120 points away, and then asked the cropped file for its text:

text extracted from cropped.pdf:
  | VISIBLE HEADER - keep this
  | Body text that stays inside the crop area.
  | CONFIDENTIAL-FOOTER-12345 (this is what we crop away)

The footer we had just cropped off came straight back out. Any copy-paste, any search, any text-extraction script recovers it. Then we un-cropped the file by resetting its CropBox to match its MediaBox — three lines of code — and the hidden content was fully visible again.

So: never crop a PDF to hide a signature, a salary, an address or a name. That is not redaction, it is a sticky note. Real redaction removes the underlying content, and the only reliable free route is to flatten the page into an image so there is nothing left to recover. We checked that too — after rasterising, the extractable text length was 0 characters. Worth knowing that it costs you selectable text and searchability across the whole page.

The file will not get smaller

People crop expecting to save space. Here is the measurement: a page with a large photo on it, cropped down to about 18% of its original area.

original file    1,251,282 bytes
cropped file     1,250,884 bytes
change                 -0.0%

Four hundred bytes out of 1.25 MB. The entire photograph is still embedded, at full resolution, because the CropBox only changed what gets displayed. If your goal is a smaller file, cropping is the wrong lever entirely — use Compress PDF, which actually re-encodes the images, or Split PDF to drop whole pages you do not need.

• The crop disappeared after saving. Almost always an export that rebuilt the file from the MediaBox and discarded the CropBox. Save normally (Command + S in Preview) rather than using Export or Print to PDF.
• It looks cropped on screen but prints full-size. Some older printer drivers honour the MediaBox and ignore the CropBox. Check "Fit to printable area" in the print dialog, or flatten the page first.
• Only page 1 is cropped. You did not select all pages — see the table above.
• The crop is offset from where you dragged. The page almost certainly has rotation applied. Rotation and cropping interact badly, because the crop is measured in the page's unrotated coordinates. Fix the rotation first with Rotate PDF, save, reopen, then crop.
• Another app shows the uncropped page. A viewer that ignores the CropBox will show the full MediaBox. Nothing is broken — this is the same fact as the section above, visible from a different angle.
• The scanned border is grey, not white, and auto-detect misses it. Margin detectors look for pure white. Raise the contrast or set the margins by hand.

A note on FileNaut: we do not currently have a dedicated PDF cropper — we would rather say so than send you to a page that cannot do the job. What we do have that is genuinely useful here: PDF Editor for changing what is on the page, Split PDF for removing whole pages, Rotate PDF for orientation, and Compress PDF for the file-size problem that cropping does not solve. All of them run in your browser — the file never gets uploaded.