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How to compress a PDF on Mac (with or without Preview)

9 October 2026 · 4 min read

To compress a PDF on a Mac, open it in Preview, choose File → Export, set Quartz Filter to Reduce File Size and save it under a new name. That is free and already installed, but it gives you no control over quality. If the result is blurry or hardly smaller, a browser tool with a choice of modes does better, and the one below works without uploading the file.

The short version

1. Check how big the file is: select it in Finder and press Command-I.
2. Try Preview's Reduce File Size filter first; it takes ten seconds.
3. If the pages come out soft or the file barely shrinks, use the Compress tool in Safari or Chrome and pick a mode.
4. Open the result and zoom in before you send it. Keep the original.

How do I compress a PDF with Preview?

1. Open the PDF in Preview (double-click it, or Control-click and choose Open With → Preview).
2. Choose File → Export. Not Export as PDF: that one has no options.
3. Make sure Format is PDF, then open the Quartz Filter menu and choose Reduce File Size.
4. Give the file a new name, for example add -small, and click Save.

The filter scales down and recompresses every image in the file. It does not ask how far to go, so the same setting is applied to a photo, a scanned page and a logo alike.

Why did Preview make my PDF blurry, or bigger?

Two things commonly go wrong with Reduce File Size:

• Scans and photos turn soft. The filter is aggressive with images, so small print on a scanned page can become hard to read. That matters for contracts, forms and anything someone has to read on paper.
• Text-only PDFs do not shrink. A PDF exported from Word or Pages is mostly text and fonts, which the filter leaves alone. Re-saving such a file can give you roughly the same size, sometimes a little larger.

Advanced users can make a gentler version of the filter in ColorSync Utility (in Applications → Utilities), under Filters, by duplicating Reduce File Size and changing its image settings. It works, but it is fiddly for a one-off.

How do I compress a PDF on a Mac without uploading it?

Most compression websites send the PDF to their server and send a smaller one back. The pdfagents.ai Compress tool runs inside the browser tab instead, so the file is processed on your Mac and nothing is uploaded. It works in Safari, Chrome and Firefox with nothing to install.

1. Open the Compress tool and drop the PDF on it. It tells you the current size.
2. Choose a mode:
   • Light: keep text selectable. Re-saves the file more compactly. The text stays text. It helps most on files that were saved inefficiently; if it cannot gain anything, it says so instead of handing you the same file.
   • Strong: pages become images. Every page is redrawn as a JPEG at the quality you pick: Good (print), Small (screen) or Tiny (preview). This is the mode that shrinks scans and photo-heavy files a lot.
3. Download the result. It is named after your file with -compressed at the end.

The honest trade-off of the strong mode: because each page becomes a picture, you can no longer select or search the text, links stop working and form fields are gone. If the file needs to stay searchable, run OCR on the compressed result. The tool has no "make it exactly 2 MB" setting; if Good is still too big, try Small.

Which method should I use?

• A scan or a phone photo of a document: the strong mode at Small or Good, so you choose how sharp the result is.
• A report exported from Word or Pages: the light mode. If it says there is nothing to gain, the file is already about as small as a text PDF gets.
• A brochure full of photos: try Preview's filter and the strong mode, and keep whichever looks better at the size you need.
• A signed contract or a form someone must fill in: the light mode, or leave it alone. The strong mode removes form fields.

If it is still too big

• Remove pages nobody needs. Delete pages such as blank backs of scanned sheets.
• Send it in parts. Split the PDF and attach the parts to separate emails.
• Check the email limit. Compressing a PDF for email covers the common attachment limits and what to do when you are just over them.

Questions people ask

How do I compress a PDF on a Mac for free?

Open the PDF in Preview, choose File, then Export, pick Reduce File Size under Quartz Filter and save under a new name. If the result is blurry or barely smaller, use a browser tool such as the pdfagents.ai Compress tool, which runs in the browser tab and offers a light mode that keeps text and a strong mode with three quality levels; downloads are free.

Why is the Export as PDF option missing the Reduce File Size filter?

Preview has two menu items. File, Export as PDF saves a plain copy without options. The Quartz Filter menu with Reduce File Size is only in File, Export, with PDF chosen as the format.

Why did Preview make my PDF blurry, or even bigger?

The Reduce File Size filter recompresses and scales down every image without asking about quality, so scans and photos can come out soft. A PDF that is mostly text has little to compress, and re-saving it can produce a file of about the same size or slightly larger. Keep the original until you have checked the result.

Can I compress a PDF on a Mac without uploading it?

Yes. Preview works offline, and the pdfagents.ai Compress tool runs inside the browser tab, so the PDF is processed on your Mac and is not uploaded.