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How to compress a PDF on Mac without losing quality

Updated October 2026 · 6 min read

Where PDF size comes from

Text and vector drawings take very little space. Big PDFs are almost always big because of images: photos, or — in scanned documents — every page being a picture. Good PDF compression therefore recompresses only the images and leaves text and vectors untouched, so text stays sharp and selectable.

That also explains a common frustration: if a PDF is mostly text and fonts, no tool can shrink it much without damaging it. A “compressed” 46 MB file that comes out at 43 MB usually means there was little image data to work with.

Option 1: Preview (built in)

Open the PDF in Preview → File → Export → Quartz Filter → Reduce File Size. It’s free and quick, but the built-in filter downsamples images hard and uses strong JPEG compression. Scans often come out blurry, and occasionally the file even gets bigger.

Option 2: a better Quartz filter with ColorSync Utility

1. Open ColorSync Utility (in Applications → Utilities) and click Filters.
2. Duplicate “Reduce File Size” using the menu on the right of the filter, and rename the copy, e.g. “Reduce File Size 150 dpi”.
3. Expand Image Sampling: set a resolution around 150–200 pixels/inch, and raise the maximum size limit.
4. Expand Image Compression: choose JPEG and move the quality slider toward the high end.
5. Back in Preview, export again and choose your new filter.

150 dpi keeps typical printed text readable; use 200 dpi for small print or forms you’ll need to print.

Option 3: Ghostscript (free, command line)

If you use Homebrew, install Ghostscript with brew install ghostscript, then:

gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH -sOutputFile=smaller.pdf original.pdf

/ebook targets about 150 dpi images; /printer about 300 dpi; /screen about 72 dpi (smallest, often too blurry for scans). Ghostscript rewrites the whole file, so check links and form fields afterwards.

Check the result before you send it

• Same number of pages as the original.
• Text is still selectable and searchable (try ⌘F).
• Zoom to 100% on the smallest print and on any signatures or stamps.
• No blank pages.
• Keep the original — never compress your only copy.

PDF support in SizeFit

SizeFit compresses PDFs to a target size with the same approach as its video side: it recompresses only embedded images until the file fits, keeps text selectable, then checks page count, extracted text and every page’s appearance against the original — and says clearly when a PDF can’t shrink meaningfully instead of handing back a near-identical file.