Compress PDF
Reduce file size by up to 80% without losing quality. No watermarks, no sign-up.
Balanced — good compression with decent quality
Upload a PDF to compress
How It Works
Upload your PDF
Drag and drop or click to select. Files up to 25 MB on the free plan.
Choose compression level
Low (archive), Medium (email), or High (mobile) — Medium works best for most files.
Download compressed PDF
Processing takes under 5 seconds. Your file is deleted from our server immediately after.
Why SynthPDF?
Up to 80% smaller
Image-heavy PDFs can shrink from 40 MB to under 6 MB — small enough to email anywhere, with no visible quality difference on screen.
Text stays perfectly crisp
Only embedded images are re-sampled. Text is stored as vectors and is never touched — your typography stays sharp at any zoom level.
No watermarks, ever
The compressed PDF is clean. We never add branding or logos to your output, on any plan.
3 compression levels
Low for archival quality, Medium for email sharing, High for mobile and web — choose the tradeoff that fits your use case.
Files deleted immediately
Your PDF is processed over HTTPS and deleted from our servers within 30 minutes. We never read or retain document content.
Works on any device
Compress PDFs on Mac, Windows, iPhone, Android, or any modern browser — no app download required.
Why PDF File Size Matters
Large PDFs cause real problems: email clients reject attachments over 10 MB, cloud storage fills up fast, and slow download times frustrate mobile users. A 40 MB scanned contract can typically be compressed to under 6 MB with no visible quality loss — making it shareable anywhere.
How PDF Compression Works
A PDF contains three main components: text (vector data), images (raster data), and fonts. Text is already highly compact — it's stored as mathematical curves. Images are the primary source of file size, often accounting for 80–95% of a large PDF.
Compression targets images by:
- Downsampling — reducing image resolution from 300 DPI to 96–150 DPI (sufficient for screens)
- Re-encoding — converting lossless PNG images inside the PDF to optimised JPEG
- Stripping metadata — removing embedded thumbnails, XMP data, and duplicate font subsets
Text and vector content is never touched. Your typography stays crisp at any zoom level.
Which Compression Level Should You Choose?
- Low (10–30% reduction): Archival, print, or documents where image sharpness is critical. Minimal visual change.
- Medium (40–60% reduction): The best default for email and sharing. Images still look sharp on screen.
- High (60–80% reduction): Mobile, web publishing, or when file size is the top priority. Some image softening on close inspection.
Common Use Cases
- Scanned documents — scanner output is often 150–300 DPI with uncompressed images. High compression brings these from 30 MB to under 4 MB.
- Photo-heavy reports — annual reports, real estate brochures, and design portfolios compress the most.
- Email attachments — most email servers limit attachments to 10–25 MB. Medium compression ensures delivery.
- Court and government filings — many filing systems have 5–10 MB limits per document.
Privacy: Your Files Are Deleted Immediately
Compression requires server-side processing — we use a cloud rendering engine to re-encode image data. Your file is uploaded over HTTPS, compressed, and deleted from our servers within 30 minutes. We never read or retain document content. For highly sensitive documents, use our browser-only tools (merge, split, protect) which never leave your device.
SynthPDF vs. Competitors — PDF Compressor Comparison
| Feature | SynthPDF | iLovePDF | Smallpdf | Adobe Acrobat |
|---|---|---|---|---|
| Price | Free | Free (limited) | Free (limited) | $19.99/mo |
| Max compression | 80% | 70% | 60% | 80% |
| Compression levels | 3 | 2 | 1 | 3 |
| No watermarks | ✅ | ✅ | ❌ (free tier) | ✅ |
| File size limit (free) | 25 MB | 15 MB | 5 MB | None |
| Files deleted after | 30 min | 2 hours | 1 hour | Varies |
Frequently Asked Questions
No. Text is stored as vectors in PDFs and is never touched. Only embedded images are re-sampled, so your typography stays crisp.
Free users can compress files up to 25 MB. Pro plan supports up to 100 MB, Max up to 150 MB, and UltraMax up to 200 MB.
Files are processed on our server and automatically deleted within 30 minutes. We never read or share your document contents.
You need to remove the password first using our Unlock PDF tool, then compress it.
Typical results: 10–30% on Low, 40–60% on Medium, and 60–80% on High. Image-heavy PDFs compress more than text-only documents.
Related Tools
Want to learn more?
Read: How to Compress a PDF Without Losing Quality →