Compress a PDF on Mac in one second.

What actually makes a PDF big

Almost always it’s images: scanned pages, photos and slide backgrounds saved at full camera resolution. Text and vector drawings are tiny by comparison. A good compressor shrinks the images and leaves the text alone, so the file gets smaller while the words stay crisp when you zoom in or print.

That’s the difference you see between Preview’s Reduce File Size filter and Sheaf. Preview applies one aggressive setting to everything, which is why text in scans and charts often turns soft. Sheaf compresses scans and photos hardest and keeps text as text.

Choosing a size

• Balanced (default) is made for email: most files drop 70–90% and still look right on screen and on paper.
• Fit 25 MB keeps going until the file fits the usual email limit; Fit 5 MB targets upload forms.
• If a file can’t get small enough without hurting it, split it into email-sized parts instead.

Real numbers

On a Mac with Apple silicon, a 42.7 MB slide deck becomes 3.3 MB in about 0.6 seconds (Balanced). Your results depend on what’s inside the PDF: a scan of 30 pages shrinks far more than a text-only report that’s already small.

Why not use a website?

Online compressors work, but the file is uploaded to someone else’s server. That’s a bad trade for contracts, IDs, tax returns, medical records and bank statements, which are exactly the files that tend to be large scans. Sheaf never uploads anything; it works with Wi-Fi off.