Make a PDF smaller on a Mac, without making it unreadable
Preview can shrink a PDF in one click, but often too far. How to reduce PDF size on a Mac with Preview, and a better option when text needs to stay sharp.
A 40 MB PDF will not attach to an email, or a folder of scanned documents takes several GB. Most of the size is usually images inside the PDF, and those can be compressed.
1. Preview: one click
- Open the PDF in Preview.
- Choose File, Export.
- In Quartz Filter, choose Reduce File Size.
- Save with a new name, so the original is kept.
This works well for photo-heavy PDFs. The catch: it compresses aggressively, and scanned text can become blurry. Always open the result and zoom in before deleting the original.
2. Ghostscript: better control
If Preview's result is too blurry, the free Ghostscript tool, installed with Homebrew, gives quality levels:
brew install ghostscript
gs -sDEVICE=pdfwrite -dPDFSETTINGS=/ebook -dNOPAUSE -dBATCH -sOutputFile=smaller.pdf input.pdf| Setting | Quality | Size |
|---|---|---|
| /screen | Low, fine on screen | Smallest |
| /ebook | Good for reading | Small |
| /printer | High | Larger |
| /prepress | Highest | Largest |
/ebook is the usual sweet spot.
3. Print to PDF again
Opening a PDF and choosing File, Print, Save as PDF sometimes drops unused data and makes a smaller file. Results vary, and form fields and links can be lost.
Check the result
ls -lh input.pdf smaller.pdfScanned documents are usually the biggest PDFs on a Mac. Scanned documents taking up space covers scanning at the right settings in the first place.
Common questions
How do I reduce a PDF file size on a Mac for free?
Open it in Preview, choose File, Export, set Quartz Filter to Reduce File Size, and save with a new name. Check the result is still readable.
Why is my PDF blurry after reducing the size in Preview?
Preview's Reduce File Size filter compresses images heavily. Ghostscript with the /ebook setting usually keeps text sharper.
Why is my PDF so large?
Usually because it contains high resolution images, such as scans or photos. Text alone takes very little space.