How to Compress PDF on Mac and iPhone — Preview, Online, and Free Methods

Mac has a built-in PDF compressor (Preview), but it gives you zero control over quality. Here is how to use it — plus a better method when Preview makes your PDFs blurry.

Mac PDF Compression Methods

Method	Control Over Quality	Compression Level	Install Required	Best For
Preview (built-in)	✗ None — one setting	~Aggressive	✓ None — comes with Mac	Quick compression of text docs
Online tool (Safari)	✓ Adjustable	Adjustable	✓ None — open in browser	Photo-heavy PDFs, precise control
PDF Expert app	✓ Adjustable	Adjustable	✗ App Store ($80/year)	Heavy PDF users who need editing too
Automator + Quartz	~Custom filters possible	Custom	✓ Built-in (advanced)	Batch processing multiple PDFs
Ghostscript (Terminal)	✓ Full control	Any level	✗ brew install ghostscript	Power users, scripting

Method 1: Preview (Built-In, Free)

1. Right-click the PDF → Open With → Preview
2. Click File → Export (NOT "Save" or "Save As")
3. In the Quartz Filter dropdown, select "Reduce File Size"
4. Choose where to save → click Save
5. Check the result — if images look blurry, use the online method instead

Important: Use "Export" not "Save." "Save" overwrites your original. "Export" creates a new compressed copy.

When Preview's Compression Is Too Much

Preview often reduces images to 72 DPI with high JPEG compression. Results:

PDF Type	Preview Result	Acceptable?
Text-only (no images)	30-50% smaller, text perfectly sharp	✓ Yes
Text + simple charts	40-60% smaller, charts slightly softer	✓ Usually yes
Scanned document	60-80% smaller, text may be fuzzy	~Sometimes
Photo-heavy report	70-90% smaller, photos noticeably blurry	✗ Often not
Design portfolio	80%+ smaller, images degraded	✗ No

Method 2: Online Compressor (Better Quality Control)

1. Open PDF compressor in Safari
2. Drag your PDF into the tool (or click to browse)
3. Adjust compression level — start with medium
4. Check output size and quality
5. Download the compressed file

Advantage over Preview: you choose the compression level. Need it smaller? Increase compression. Need better quality? Decrease compression. Preview gives you no choice.

iPhone and iPad Compression

iOS has no built-in PDF compression. Your options:

1. Safari + online tool (free, recommended): Open our compressor in Safari, tap "Choose File," select from Files app, compress, download
2. Shortcuts app: Create an automation that uses the "Make PDF" action with reduced quality — technical but works offline
3. Third-party apps: PDF Expert, Smallpdf, iLovePDF all have iOS apps with compression

Mac PDF Workflow

1. Try Preview first — if quality is acceptable, you are done
2. If Preview makes it blurry, use the online compressor
3. Need to extract pages first? Split the PDF
4. Need to combine files? Merge PDFs, then compress
5. Sensitive document? Our tool processes locally — nothing leaves your Mac