PDF Compress

SKILL.md

PDF Compress

Reduce PDF file sizes for easier sharing, faster loading, and efficient storage.

Overview

This skill helps you:

Reduce PDF file sizes significantly

Balance quality vs. file size

Optimize for specific use cases (web, print, archive)

Batch compress multiple files

Understand compression trade-offs

How to Use
Basic Compression

"Compress this PDF to reduce file size"
"Make this PDF smaller for email"
"Optimize this PDF for web viewing"

With Targets

"Compress this PDF to under 5 MB"
"Reduce file size by at least 50%"
"Optimize for minimum file size"

Quality Levels

"Compress with high quality (minimal loss)"
"Compress for screen viewing"
"Maximum compression, quality not critical"

Compression Levels

Presets

Level
Target Use
Image Quality
Size Reduction

Minimum
Archival
Original
5-15%

Low
Print
Near original
15-30%

Medium
General use
Good
30-50%

High
Email/Web
Acceptable
50-70%

Maximum
Preview only
Reduced
70-90%

Use Case Recommendations

Use Case
Recommended Level
Reason

Print production
Minimum/Low
Quality critical

Email attachment
Medium/High
Balance size/quality

Web download
High
Fast loading

Quick preview
Maximum
Speed priority

Archive
Low
Long-term quality

Presentation
Medium
Good on-screen

Compression Techniques

Image Optimization

## Image Compression Settings

### Resolution Reduction
| Target | DPI | Use For |
|--------|-----|---------|
| Screen | 72 | Web viewing |
| eBook | 150 | Digital documents |
| Print-basic | 200 | Office printing |
| Print-quality | 300 | Professional print |
| Original | N/A | No reduction |

### Format Conversion
| From | To | Savings | Quality Impact |
|------|-----|---------|----------------|
| TIFF | JPEG | 70-90% | Some loss |
| PNG | JPEG | 50-80% | Some loss |
| BMP | JPEG | 90%+ | Some loss |
| JPEG | JPEG (recompress) | 20-50% | Cumulative loss |

### Quality Levels
| Setting | JPEG Quality | Visual Impact |
|---------|--------------|---------------|
| Maximum | 90-100 | Imperceptible |
| High | 75-89 | Minimal |
| Medium | 50-74 | Noticeable on zoom |
| Low | 25-49 | Visible artifacts |

Content Optimization

## Additional Optimizations

### Font Optimization
- [ ] Subset fonts (remove unused characters)
- [ ] Convert to standard fonts where possible
- [ ] Remove duplicate font instances

### Structure Optimization
- [ ] Remove unused objects
- [ ] Clean up metadata
- [ ] Linearize for web (fast web view)
- [ ] Remove bookmarks (optional)
- [ ] Remove comments/annotations (optional)

### Content Removal (Caution)
- [ ] Remove hidden layers
- [ ] Remove JavaScript
- [ ] Remove form fields
- [ ] Remove embedded files

Output Report

Compression Report

## PDF Compression Report

### File Summary
| Metric | Before | After | Change |
|--------|--------|-------|--------|
| **File Size** | 45.2 MB | 8.7 MB | -81% |
| **Pages** | 120 | 120 | - |
| **Images** | 89 | 89 | - |

### Compression Applied
| Technique | Savings |
|-----------|---------|
| Image downsampling (150 DPI) | 28.5 MB |
| JPEG compression (75%) | 5.2 MB |
| Font subsetting | 1.8 MB |
| Object cleanup | 1.0 MB |
| **Total Savings** | **36.5 MB (81%)** |

### Quality Assessment
| Aspect | Rating | Notes |
|--------|--------|-------|
| Text clarity | ⭐⭐⭐⭐⭐ | No change |
| Image sharpness | ⭐⭐⭐⭐ | Slight softening |
| Color accuracy | ⭐⭐⭐⭐⭐ | Preserved |
| Zoom quality | ⭐⭐⭐ | Pixelation at 400%+ |

### Recommendations
✅ Suitable for: Email, web, screen viewing
⚠️ Not recommended for: High-quality print, archival

Optimization Plan

## Compression Strategy: [Document Name]

### Current State
- File size: 150 MB
- Pages: 200
- Issue: Too large for email (limit: 25 MB)

### Target
- Max size: 20 MB
- Maintain readability

### Recommended Approach
1. **Images**: Reduce to 150 DPI, JPEG 70%
   - Expected savings: ~100 MB
2. **Fonts**: Subset embedded fonts
   - Expected savings: ~5 MB
3. **Cleanup**: Remove metadata, optimize structure
   - Expected savings: ~5 MB

### Expected Result
- Final size: ~20 MB
- Quality: Good for screen/general use

Batch Compression

Batch Job Template

## Batch Compression Job

### Input
- **Folder**: /documents/reports/
- **Files**: 45 PDFs
- **Total Size**: 2.3 GB

### Settings
- Compression level: Medium
- Target: Email-friendly (<10 MB each)
- Image DPI: 150
- JPEG quality: 75%

### Progress
| File | Original | Compressed | Reduction |
|------|----------|------------|-----------|
| report_q1.pdf | 85 MB | 12 MB | 86% |
| report_q2.pdf | 120 MB | 18 MB | 85% |
| report_q3.pdf | 95 MB | 14 MB | 85% |
| ... | ... | ... | ... |

### Summary
| Metric | Value |
|--------|-------|
| Files processed | 45 |
| Total before | 2.3 GB |
| Total after | 380 MB |
| Average reduction | 83% |
| Files under 10 MB | 42/45 |

### Large Files (Need Review)
| File | Size | Recommendation |
|------|------|----------------|
| annual_photos.pdf | 25 MB | Split or higher compression |
| tech_diagrams.pdf | 18 MB | Reduce image count |
| charts_hires.pdf | 15 MB | Acceptable |

Quality Comparison

Before/After Guide

## Quality Comparison Guide

### Image Quality at Different Levels

**Original (300 DPI, no compression)**
- Sharp at all zoom levels
- File size: Large

**High Quality (200 DPI, JPEG 85%)**
- Sharp at 100-200% zoom
- Minor softening at high zoom
- File size: Medium-large

**Medium Quality (150 DPI, JPEG 70%)**
- Good at 100% zoom
- Noticeable softening at 200%+
- File size: Medium

**Low Quality (96 DPI, JPEG 50%)**
- Acceptable at 100%
- Pixelation visible
- File size: Small

### Text Remains Sharp
Note: Text (when vector) remains crisp at all compression levels.
Only embedded text images are affected.

Tool Recommendations

Online Tools

SmallPDF: Easy, good quality

ILovePDF: Free, batch support

PDF24: Configurable options

Adobe Online: Professional quality

Desktop Software

Adobe Acrobat Pro: Best control

Foxit PDF Editor: Good alternative

PDF-XChange: Many options

Preview (Mac): Basic, built-in

Command Line

Ghostscript: Powerful, scriptable

qpdf: Fast, lossless options

pdfcpu: Modern Go tool

img2pdf: Image-specific

Limitations

Cannot perform actual compression (provides guidance)

Some PDFs have minimum compressible content

Scanned documents are mostly images

Already compressed PDFs have less savings

Extreme compression affects quality

Vector graphics don't compress much