How to Compress a PDF on Mac Without Uploading It (2026)

The fastest way to shrink a PDF on a Mac is already built into the operating system — but the one-click version is also the reason so many "compressed" PDFs come out blurry. macOS gives you several ways to make a PDF smaller, and they trade off differently between file size, image quality, and how much fuss is involved. None of them require handing your document to a website.

That last point matters more than it sounds. When you search for a PDF compressor and land on one of the big web tools, your file gets uploaded to a stranger's server to be processed. For a flyer, who cares. For a signed contract, a tax return, a medical record, or a bank statement, you shouldn't have to. On a Mac, you don't. Here are the four real methods, from blunt-and-instant to precise-and-private.

First, why "just use an online compressor" isn't the default answer

The popular web compressors work by uploading. Smallpdf and iLovePDF both process your PDF on their own servers and then delete it after a retention window — that's stated plainly in their privacy policies. It works, and for non-sensitive documents it's genuinely convenient. But it means the file leaves your computer, travels across the internet, and sits on someone else's infrastructure for a while. Every method below keeps the document on your Mac (or, for the browser option, inside your own browser tab) from start to finish.

Method 1 — Preview's built-in "Reduce File Size" (free, instant, blunt)

Every Mac ships with Preview, and it can compress a PDF in about four clicks:

1. Open the PDF in Preview.
2. Go to File > Export (not "Export as PDF").
3. Set Format to PDF.
4. In the Quartz Filter dropdown, choose Reduce File Size, then click Save.

That's the whole trick, and it's why it's the answer you see everywhere. The problem is what it does under the hood: this single filter downsamples every image in the document aggressively, and Apple gives you no slider to dial it back. On a text-only PDF you'll never notice. On anything with photos or scanned pages, the images can come out noticeably soft — sometimes to the point of being hard to read.

Method 2 — A custom Quartz filter for controlled compression (still native)

Preview's bluntness isn't a hard limit — it's just the one preset Apple ships. You can build your own Quartz filter with the resolution and quality you choose, and it will show up in that same Preview dropdown. It's a one-time setup using ColorSync Utility, which is already on your Mac:

1. Open ColorSync Utility (Applications > Utilities).
2. Click the Filters tab.
3. Find Reduce File Size and click the duplicate icon on its right to copy it.
4. Click the gear icon to rename the copy something memorable, like "Reduce File Size 150 DPI".
5. Expand the filter. Under Image Sampling, set the resolution (150 DPI is a good balance for readable images; 100 DPI shrinks more). Under Image Compression, set the quality higher than the default.
6. Close ColorSync Utility. Your custom filter now appears in Preview's File > Export > Quartz Filter list.

Now you get most of Preview's convenience with real control over the size-versus-quality tradeoff. For most people who found Preview's default too destructive, this is the sweet spot.

Method 3 — Ghostscript in Terminal (maximum control, for power users)

If you're comfortable in the Terminal and want the finest control — or you need to batch-compress many files — Ghostscript is the tool the pros use. Install it once with Homebrew:

brew install ghostscript

Then compress a PDF with a single command:

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 \
   -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH \
   -sOutputFile=out.pdf in.pdf

The magic is in -dPDFSETTINGS, which picks a target resolution:

Swap /ebook for any of the others depending on how aggressive you want to be. Because it runs from the command line, you can also loop it over a whole folder of PDFs.

Method 4 — Compress it in your browser, with nothing uploaded

Preview needs a specific macOS version's UI, a custom Quartz filter takes setup, and Ghostscript means the Terminal. If you want something that works on any Mac with zero install and zero risk of your file being sent anywhere, use a client-side browser tool. FilePulp's PDF compressor runs entirely inside your browser tab — the document is read into memory locally, compressed with JavaScript, and saved back to your disk. It never travels to a server, which is the whole point of the privacy-first approach: you can verify it in your browser's network tab, no uploads happen.

It's the right call for a sensitive document you'd rather not hand to an upload site, for an older or locked-down Mac where you can't install software, or when you just want the job done in one drag-and-drop. For the heaviest image downsampling, Ghostscript or a custom Quartz filter still give you more knobs — but for most everyday PDFs, in-browser is the fastest private option.

Which method should you use?

The one rule that holds across all of them: PDF size is almost always about images, not text. If your file is a scan or full of photos, you shrink it by downsampling those images — that's what every method here is really doing. If it's mostly text and still large, compression won't buy you much, and the real fix is elsewhere in how the file was made.