PDF Compression Guide: Shrink File Size Without Losing Clarity
How to compress PDFs effectively: images, fonts, and settings that matter.
PDF Compression Fundamentals
Compression Methods Explained
Image Compression in PDFs
Text and Font Optimization
Advanced Compression Techniques
Quality vs Size Balance
| Method | Best For | Compression Ratio | Quality Impact | Use Case |
|---|---|---|---|---|
| JPEG | Photos/Images | High | Lossy | Web/Email |
| ZIP | Text/Graphics | Medium | Lossless | Archival |
| LZW | Mixed Content | Medium | Lossless | General |
| CCITT | Scanned Text | Very High | Lossless | Fax/Archive |
Checklist
- Analyze document content type
- Choose appropriate compression method
- Optimize image resolution and quality
- Subset fonts to used characters only
- Remove unnecessary metadata
- Test compression on sample pages
- Verify quality after compression
- Check file size reduction
- Test on different PDF viewers
- Document compression settings used
Troubleshooting
- Poor image quality after compression: Increase JPEG quality setting, use ZIP for graphics
- Text becomes unreadable: Use lossless compression, check font embedding
- File size not reduced enough: Downsample images, remove unused fonts, clean metadata
- Compression takes too long: Use faster compression settings, process in batches
Use cases
Email attachment optimization
1) Compress images to 150 DPI
2) Use JPEG medium quality
3) Remove unnecessary metadata
4) Target file size under 5MB
Web document delivery
1) Use fast web view optimization
2) Compress images for web resolution
3) Linearize PDF for streaming
4) Test loading speed
Archive storage
1) Use lossless compression
2) Maintain original quality
3) Remove unnecessary elements
4) Document compression settings
Glossary
- Downsampling: Reducing image resolution to decrease file size
- Font subsetting: Including only used characters from a font
- Linearization: Optimizing PDF structure for web streaming
- Object streams: Compressed containers for PDF objects
- Cross-reference table: PDF structure for locating objects
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FAQ
Typically 150 DPI balances clarity and size for screens.
Check embedded fonts and uncompressed images; remove unused assets.