What makes a PDF compressor actually good

What compression is actually doing

Most of a PDF's size comes from embedded images. Compressing a PDF mainly means re-encoding those images at a lower resolution or quality setting — text and vector content usually take up very little space by comparison. That's why a scanned, image-heavy PDF compresses dramatically, while a mostly-text document may barely shrink at all.

What to look for

• Adjustable quality — a single fixed compression level either wrecks image-heavy files or barely touches text-heavy ones.
• No upload for sensitive documents — compression is often used on documents like scanned IDs or contracts, which is exactly the kind of file you don't want touching a third-party server.
• Predictable results — you should be able to see the resulting size before committing to a download.

Compressing with pdfvelo

1. Open the Compress PDF tool.
2. Drop in your file and pick a quality level.
3. Compare the estimated new size against the original.
4. Download the compressed file.

Frequently asked questions