How to crop a PDF on a Mac
Preview crops a PDF for free — show the Markup toolbar, drag a rectangle over what you want to keep, press Command-K. Or crop in a browser tab, one crop for all pages or a different one per page.
Cropping a PDF is one of the jobs a Mac does on its own. Preview is already installed, and it trims a page well for free — no download, no account. This is the honest version: the built-in Preview route step by step, the two reasons people get stuck in it, the one thing cropping on a Mac does not do that everyone assumes it does, and the specific cases where a browser tab is the better free answer.
Is there a crop tool on a Mac?
Yes. Preview, the app that already opens every PDF on your Mac, crops pages for free. Open the file, click the Show Markup Toolbar button, choose the Rectangular Selection tool, drag over the part you want to keep, then press Command-K or choose Tools then Crop. Save to apply it.
How do I crop a PDF in Preview on a Mac?
Open the PDF in Preview
Double-click the file, or drag it onto the Preview icon. Preview is the default PDF viewer, so this is usually just a double-click.
Show the Markup toolbar
Click the Show Markup Toolbar button — the pencil-tip-in-a-circle icon near the top right. The crop tools live here, not in the main toolbar, which is why they are easy to miss.
Select what you keep
Click the Rectangular Selection tool, then drag a box over the part of the page you want to keep. You are selecting the keeper, not the part to throw away.
Crop and save
Press Command-K, or choose Tools then Crop. Then choose File then Export as PDF so your original stays intact.
Why can I not crop a PDF in Preview on my Mac?
Two things trip almost everyone. First, the Crop command stays greyed out until you have actually dragged a selection with the Rectangular Selection tool — no box, no crop. Second, Preview crops the page you are on; to crop every page of a long document you select all the thumbnails in the sidebar first, and even then people report Preview re-sizing the exported pages to letter or A4 with white padding around the crop. If per-page control or an exact result matters, that is the moment to reach for a browser tool instead.
Does cropping on a Mac remove what you trimmed?
No, and this is the part that catches people out. Cropping on a Mac — in Preview or in any browser tool, ours included — sets a crop box, a rectangle telling viewers which part of the page to show. The trimmed content is still in the file, byte for byte, and anyone can reset the crop and get it back. Preview's crop is non-destructive by design, which is exactly the problem when you meant to remove something rather than tidy it. That distinction is fine for trimming margins and a genuine trap if you were cropping to hide something. Cropping a PDF does not remove anything covers how to make it truly gone.
When is a browser tool the better free option on a Mac?
When you want a different crop on each page without the thumbnail-selection dance, when you want the cropped page to stay exactly the size of your rectangle rather than being re-padded on export, or when the Mac is not yours to leave files on. Crop PDF does all of that in Safari or Chrome, the same way on any macOS version, and builds the file on your Mac.
Open the tool
Open Crop PDF. It is an ordinary web page — nothing to install and no account to make.
Pick a mode
On a multi-page file you choose "Same crop, all pages" or "Crop each page". Pick before you start dragging — they do genuinely different things.
Drag the rectangle inwards
Pull the handles in over the page preview. The area outside dims so you see what you are trimming. A page whose rectangle still covers the whole page is left untouched, because a full-page crop is not a crop.
Apply
Click Apply crop. The new crop box is written on your Mac and the file downloads as yourname_cropped.pdf.
Will cropping change a page that is rotated or already cropped?
It crops what you actually see, not the raw page underneath — a distinction that quietly breaks a lot of crop tools. If a page is rotated ninety degrees, the rectangle you drag on the sideways preview lands where you drew it, not turned the wrong way. If a page already has a tighter crop box, your new crop nests inside it rather than snapping back to the full sheet, so a print PDF with bleed does not suddenly reveal its trim area. We verified both by reading the output back with a separate PDF engine, not the one that wrote it.
All of this runs on the Mac in front of you. How to crop a PDF is the general walkthrough for any device, and what a PDF page actually is explains the media box, crop box and rotation underneath — the three that have to agree for a crop to land where you meant.
