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pdf-compress skill

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/skills/lijie420461340/pdf-compress

This skill helps you reduce PDF file sizes while balancing quality for web, email, and archival use.

npx playbooks add skill openclaw/skills --skill pdf-compress

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SKILL.md

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---
name: PDF Compress
description: Reduce PDF file size while maintaining acceptable quality
author: claude-office-skills
version: "1.0"
tags: [pdf, compression, optimization, file-size, performance]
models: [claude-sonnet-4, claude-opus-4]
tools: [computer, file_operations]
---

# 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
```markdown
## 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
```markdown
## 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
```markdown
## 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
```markdown
## 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
```markdown
## 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
```markdown
## 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

Overview

This skill reduces PDF file size while preserving acceptable visual and text quality. It offers preset compression levels, image and font optimizations, and batch processing workflows to make sharing, storage, and web delivery easier. The goal is predictable size targets with clear trade-offs for print, web, and archive use.

How this skill works

The skill analyzes a PDF’s components (images, fonts, metadata, and structure) and applies selected optimizations such as image downsampling, JPEG recompression, font subsetting, and object cleanup. Users choose a preset or custom targets (file-size limit, DPI, JPEG quality) and the tool reports before/after metrics and quality notes. Batch mode runs the same strategy across many files and flags items needing manual review.

When to use it

Prepare PDFs for email or cloud sharing with strict size limits
Optimize large report or presentation PDFs for web download
Batch-process archives to save storage space
Create lightweight previews for document libraries
Reduce scanned-document sizes when images dominate file size

Best practices

Choose a compression preset that matches the final use (print vs web) to avoid unnecessary quality loss
Prefer DPI reduction to extreme JPEG compression when readability is critical
Subset embedded fonts and remove duplicate font instances to save space without visual impact
Review the compression report for any files flagged as ‘needs review’ or with high image loss
Keep an original archive copy if you may need high-quality prints later

Example use cases

Compress quarterly reports to under 10 MB for email distribution while preserving legible charts
Batch-optimize a folder of product manuals for fast web download with 150 DPI and 75% JPEG quality
Prepare a conference slide deck for projector display using Medium preset to balance size and on-screen sharpness
Create small preview versions of a photo-heavy portfolio using Maximum compression for rapid browsing
Run a one-time archive pass to reduce long-term storage costs while retaining acceptable text clarity

FAQ

Will this break text or searchable PDFs?

No—text that is stored as vector remains crisp; the main risks are with embedded text images or OCRed scans where image compression can reduce legibility. Choose a higher quality preset for those cases.

Can I target a specific final file size?

Yes. You can set a size target and the tool will iteratively apply DPI, JPEG quality, and other changes to approach that limit, with a report on expected trade-offs.

What file types save most from compression?

Image-heavy PDFs (scanned documents, photo portfolios) typically see the biggest reductions. PDFs already optimized or dominated by vector graphics compress less.