It depends on the content. Scanned and image-rich PDFs often shrink dramatically, while text-only PDFs are already small and compress less.

Compression mainly optimises images inside the PDF. Text stays crisp, and the visual difference is usually minimal at normal settings.

Yes. Compress PDF is completely free with no sign-up, no watermarks and no usage limits.

No. Compress PDF runs entirely in your browser, so your data never leaves your device.

Only your device's available memory — there are no server-side limits because nothing is uploaded.