How to Reduce PDF Size on Mac: 5 Methods Compared

Mac users have several options for reducing PDF file size, from built-in tools to specialized apps. Here’s a complete comparison to help you choose the right method.

Method 1: Preview (Built-in, Free)

The simplest option — Preview is already on your Mac.

How to Use

1. Open your PDF in Preview
2. Go to File → Export
3. Click Quartz Filter dropdown
4. Select Reduce File Size
5. Click Save

Results

Original Size	After Preview	Reduction
50MB scan	8MB	84%
10MB text PDF	7MB	30%
100MB photos	15MB	85%

Pros

• ✅ Free and pre-installed
• ✅ No learning curve
• ✅ Quick for single files

Cons

• ❌ No control over output size
• ❌ Often over-compresses (blurry results)
• ❌ No batch processing
• ❌ Inconsistent quality

Best For

Quick compression when quality isn’t critical.

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Method 2: SecureCompress (Target-Size)

A dedicated compression app with precise size control.

How to Use

1. Download from securecompress.app
2. Drop your PDF into the app
3. Set your target size (e.g., 25MB)
4. Click Start
5. Get a file at exactly your target size

Results

Original Size	Target	Result	Accuracy
50MB scan	25MB	24.8MB	✅
100MB scan	10MB	9.7MB	✅
200MB scan	25MB	24.5MB	✅

Pros

• ✅ Exact target size control
• ✅ Optimized for scanned documents
• ✅ 100% local processing
• ✅ Batch processing (Pro)

Cons

• ❌ Paid for full features ($19.99)
• ❌ macOS only

Best For

When you need to hit exact size limits (job portals, government forms).

Download SecureCompress →

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Method 3: Automator (Built-in, Free)

Create automated workflows for batch compression.

How to Set Up

1. Open Automator (in Applications)
2. Create new Quick Action
3. Set “Workflow receives” to PDF files
4. Add action: Apply Quartz Filter to PDF Documents
5. Select Reduce File Size
6. Save as “Compress PDF”

How to Use

1. Right-click any PDF
2. Select Quick Actions → Compress PDF
3. File is compressed in place

Pros

• ✅ Free
• ✅ Integrates with Finder
• ✅ Can process multiple files
• ✅ Customizable workflows

Cons

• ❌ Uses Preview’s compression (same limitations)
• ❌ No size control
• ❌ Setup required

Best For

Automating repetitive compression tasks.

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Method 4: ColorSync Utility (Built-in, Free)

Create custom compression filters for more control.

How to Create a Custom Filter

1. Open ColorSync Utility (in Applications/Utilities)
2. Click Filters tab
3. Click + to create new filter
4. Add Image Effects → Image Compression
5. Set JPEG quality (0.5-0.8 recommended)
6. Add Image Effects → Image Scaling if needed
7. Save with a descriptive name

How to Use

1. Open PDF in Preview
2. File → Export
3. Select your custom filter from Quartz Filter dropdown
4. Save

Pros

• ✅ Free
• ✅ More control than default Preview
• ✅ Reusable filters
• ✅ Can fine-tune quality

Cons

• ❌ Technical setup
• ❌ Still no target-size option
• ❌ Trial and error to find right settings

Best For

Users who want more control without third-party apps.

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Method 5: Command Line (Ghostscript)

Maximum control for technical users.

Installation

brew install ghostscript

Basic Usage

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 \
   -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH \
   -sOutputFile=output.pdf input.pdf

Quality Presets

Preset	Quality	Use Case
/screen	Low	Web viewing
/ebook	Medium	General use
/printer	High	Printing
/prepress	Highest	Professional

Custom Settings

gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 \
   -dDownsampleColorImages=true \
   -dColorImageResolution=150 \
   -dNOPAUSE -dQUIET -dBATCH \
   -sOutputFile=output.pdf input.pdf

Pros

• ✅ Free and open-source
• ✅ Maximum control
• ✅ Scriptable for automation
• ✅ Cross-platform

Cons

• ❌ Technical knowledge required
• ❌ No GUI
• ❌ No target-size option
• ❌ Complex syntax

Best For

Developers and power users who need scripting.

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Comparison Table

Method	Cost	Size Control	Quality Control	Batch	Ease of Use
Preview	Free	❌ None	❌ None	❌ No	⭐⭐⭐⭐⭐
SecureCompress	$19.99	✅ Exact	✅ Good	✅ Yes	⭐⭐⭐⭐
Automator	Free	❌ None	❌ None	✅ Yes	⭐⭐⭐
ColorSync	Free	❌ None	✅ Some	❌ No	⭐⭐
Ghostscript	Free	❌ None	✅ Full	✅ Yes	⭐

Which Method Should You Use?

Use Preview if:

• You need quick, one-off compression
• Quality isn’t critical
• You don’t have specific size requirements

Use SecureCompress if:

• You need to hit exact size limits
• You’re compressing for job portals or government forms
• Privacy matters (local processing)
• You compress PDFs regularly

Use Automator if:

• You compress many files regularly
• You want right-click integration
• Preview’s quality is acceptable

Use ColorSync if:

• You want more control than Preview
• You’re willing to experiment with settings
• You don’t want to install software

Use Ghostscript if:

• You’re comfortable with command line
• You need to script compression
• You want maximum control

Tips for Best Results

For Scanned Documents

1. Use grayscale mode when possible
2. 200 DPI is sufficient for most uses
3. Target 70-80% reduction for good quality

For Text-Based PDFs

1. Compression gains are limited
2. Try Preview first
3. Use SecureCompress if you need specific size

For Mixed Documents

1. Use moderate settings
2. Verify figures and images after compression
3. Keep originals until verified

Troubleshooting

Preview makes files blurry

Preview’s “Reduce File Size” is aggressive. Try:

• ColorSync with custom filter (higher quality)
• SecureCompress with larger target size

File size didn’t change much

Your PDF might be:

• Already compressed
• Text-based (limited compression potential)
• Using efficient image formats

Compression failed

• Check if PDF is password-protected
• Verify file isn’t corrupted
• Try a different method

Summary

For most Mac users:

1. Quick jobs: Use Preview
2. Exact sizes needed: Use SecureCompress
3. Batch processing: Use Automator or SecureCompress Pro
4. Maximum control: Use Ghostscript

Each method has its place. Choose based on your specific needs.

Download SecureCompress — precise PDF compression for Mac.