Files & privacy
Keep your original before compressing
Compression is lossy, so the file you started with is the only way back — plus when to choose which level.
Updated
Compression throws information away
To make a PDF smaller, something has to go: image resolution, colour detail, or embedded font data. That is fine for an upload portal and bad for your only copy of a signed contract.
Save the downloaded result under a new name and keep the original where it was. Nothing in the tool can restore quality from the compressed file.
Choosing a level
Recommended keeps text sharp and reduces image data — the right default. Extreme goes further and is meant for scans that only need to be legible, not printable at high quality.
- Screenshots and diagrams: Recommended, then look at a zoomed section.
- Phone scans of documents: Extreme usually stays readable.
- Anything going to print: keep the original uncompressed copy.
Tools mentioned
Still stuck?
Tell us the tool, the file size and the exact error text. That is usually enough to reproduce it.