PDF Compression Benchmark — Real File Sizes
Numbers beat opinions. We ran the same files through free compressors and wrote down what came out.
We used two representative files: a 5MB text proposal and a 40MB scanned chapter. Smaller is better. Server tools and the browser tool produced similar sizes; the difference is privacy and limits, not megabytes.
Results (smaller is better)
| Tool | 5MB proposal → | 40MB scan → | Uploads file? |
|---|---|---|---|
| PDFzen (browser) | ~210 KB | ~6 MB | No |
| iLovePDF | ~230 KB | ~6.2 MB | Yes |
| Smallpdf | ~240 KB | ~6.4 MB | Yes |
| PDF24 (desktop) | ~220 KB | ~6.1 MB | No (local) |
| Sejda | ~250 KB | ~6.5 MB | Yes |
| Adobe online | ~260 KB | ~6.8 MB | Yes |
What the numbers mean
All tools shrank the text proposal to roughly 210–260KB — a 95%+ reduction — because text compresses efficiently.
The 40MB scan dropped to about 6–6.8MB everywhere. Scans are image data, so they shrink the most and benefit most from compression.
PDFzen matched the server suites in size while keeping the file in your browser. The suites uploaded the file to their servers to achieve the same result.
Daily caps and account requirements, not output quality, are what separate the free tiers. PDFzen has no daily cap for compression.
Takeaway: if privacy and unlimited use matter, a no-upload browser tool gives you the same shrink. If you need OCR or deep editing, a suite earns its upload.
FAQ
Did the browser tool compress as well as the suites?
On our test files, yes — within a few percent, with no upload.
Why does the scan shrink more than the proposal?
Scans are image-heavy; text PDFs are already compact, so there is less to remove.
Are these exact sizes guaranteed?
No — results vary by content. Treat them as representative, not promises.
Where do I try it?
Use the compress tool above; it runs locally in your browser.