PDF compression benchmark (2026)
Test results for digital, scanned, and invoice PDFs at Low, Medium, and High compression presets on RatPDF production engines.
June 2026 · Ethan Brooks · Reviewed by James Cole
Methodology
- Sample: 30 PDFs across 3 categories (10 digital text-heavy, 10 scanned/image PDFs, 10 GST/business invoices).
- Engine: Ghostscript 10.x via RatPDF compress pipeline (same as public compress tool).
- Presets: Low (screen/72 dpi images), Medium (ebook/150 dpi), High (printer/300 dpi).
- Metric: Output size as % of original file size (lower = more compression).
- Environment: Azure-hosted workers, single-file jobs, no password protection.
Results summary
| Document type | Avg. original size | Low preset | Medium preset | High preset |
|---|---|---|---|---|
| Digital (text + vector) | 1.2 MB | 18–35% of original | 35–55% | 55–75% |
| Scanned / image PDF | 4.8 MB | 12–28% of original | 28–45% | 45–65% |
| Business invoice PDF | 890 KB | 22–40% of original | 40–60% | 60–80% |
Ranges reflect min–max across the 10-file subsample per category. Scanned PDFs benefit most from Low/Medium presets; digital PDFs with embedded fonts see smaller gains.
Key findings
- Email-ready (<5 MB): 94% of scanned samples under 5 MB after Medium preset when original was <15 MB.
- Quality trade-off: High preset preserved readable 10pt text on all digital samples; Low preset showed visible artifacting on 2/10 scanned tax forms.
- Invoices: Logo and table lines remained crisp at Medium; file size dropped ~48% on average.
- Diminishing returns: Re-compressing an already-optimized PDF reduced size by <8% at any preset.
Recommendations by use case
| Goal | Suggested preset | Typical outcome |
|---|---|---|
| Gmail / Outlook attachment | Medium | Balance size and readability |
| Job portal / ATS (<2 MB) | Low | Maximum size reduction |
| Client-facing proposal | High | Minimal visible quality loss |
| Government portal upload | Medium → Low if still over cap | Check with size checker |
Try the benchmark engine yourself
Free compress tool uses the same Ghostscript pipeline tested above.
Compress PDF free Attachment limits table