How to Compress a PDF on Mac — 3 Free Methods
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Method 1: Preview's "Reduce File Size" Quartz Filter
macOS Preview has a built-in compression option:
- Open the PDF in Preview.
- Go to File → Export.
- Change the Quartz Filter dropdown from None to Reduce File Size.
- Choose a new filename and click Save.
Warning: This filter aggressively downsamples images to 72 DPI, which can make photos look blurry. It's fine for reducing text-heavy PDFs but often over-compresses image-rich documents. Always review the output before sending.
Method 2: ColorSync Utility (More Control)
ColorSync Utility (free, included with macOS) lets you create a custom compression filter with a specific image resolution — less aggressive than Preview's default filter:
- Open ColorSync Utility (search via Spotlight).
- Go to the Filters tab and duplicate the "Reduce File Size" filter.
- Edit the copy: set Image Sampling to 150 DPI (instead of 72) for a better quality-size balance.
- Use this custom filter in Preview's Export dialog.
Method 3: Browser-Based Compressor
For the most predictable results on Mac, open pdfmate.io/tools/compress in Safari or Chrome. Choose Standard or Strong compression, download the result, and compare the file size. This approach gives you a quality preview before committing, and handles complex PDFs better than Preview's Quartz filter.
Which Method Gives the Best Quality?
The browser-based compressor and ColorSync custom filter both produce better results than Preview's default "Reduce File Size" filter for image-heavy PDFs. For text-only PDFs, all three methods produce virtually identical results.