Two kinds of PDF compression
Most PDFs shrink in one of two ways. The gentle way cleans up the file's internal structure — duplicate data, unused objects and inefficient storage — and keeps text selectable and searchable. This is what the High Quality, Web Optimized and Balanced levels do.
Scanned PDFs and photo-heavy reports need the stronger way: each page is re-rendered at screen resolution and saved as a compressed image. This can shrink a scanned file by 80–95%, but text in the result can no longer be selected or searched. Small Size and exact-size mode use this only when it saves a lot, and the result tells you when it was used.
We tested it: three very different PDFs
We compressed a text-only handbook, a Word report with photos, and an 8-page contract saved the way scanning apps save pages (each page a 300 DPI image):
| Original | Balanced (lossless) | Small Size | |
|---|---|---|---|
| Text handbook, 19 pages | 100 KB | 64 KB (−36%) | 64 KB (images would be bigger) |
| Report with photos, 9 pages | 2.31 MB | 2.30 MB | 625 KB (−74%) |
| Scanned contract, 8 pages | 9.49 MB | 9.48 MB | 804 KB (−92%) |
Balanced keeps text selectable and helps text PDFs, but barely touches scans and photos, because the images are the weight. Small Size re-renders pages as images, which is what shrinks scans: the 8-page scan took about 7 seconds.
Full details, including how small a scan can go and still be readable, are in our PDF compression test.
Which option should you choose?
- Typed documents, contracts, CVs: Balanced. Keeps text selectable.
- Scans, photographed pages, image-heavy reports: Small Size.
- A strict limit like 1MB or 500KB: switch to "To an exact size".
Private by design
PDFs are often contracts, bank statements or ID scans. Here, the file is opened and compressed inside your browser — it is never uploaded to a server, so there's nothing stored for anyone else to access.
Frequently asked questions
Why did my PDF only get a little smaller?
Text-only PDFs are already compact, so standard compression saves less. Big savings come from PDFs that contain scans or photos — try Small Size for those.
Will compressing a PDF lose quality?
Standard levels don't change how text looks at all. Small Size and exact-size mode render pages at screen resolution, which looks the same on screen but isn't ideal for high-quality printing.
Can I compress a password-protected PDF?
Usually not — remove the password in your PDF reader first, then compress.
Is there a page limit?
No fixed limit. Very large PDFs (hundreds of scanned pages) take longer because every page is processed on your device.