How do I compress a PDF to 400KB?

Upload your PDF, click the 400KB preset (or enter a custom size), and click Compress. ExactPDF binary-search compressor finds the highest quality that fits under 400KB — all in your browser, no upload.

Why do I need a PDF under 400KB?

400KB works for most multi-page application packets — IDs, transcripts, certificates — without forcing painful quality loss on photos.

Is 400KB small enough for email attachment limits?

Yes — every major email provider (Gmail, Outlook, Yahoo, Proton, corporate Exchange) accepts attachments far larger than 400KB. 400KB is for portals with explicit caps, not email.

Is my PDF safe during compression?

Yes. ExactPDF compresses your PDF entirely in your browser using JavaScript and WebAssembly. The file never leaves your device — no upload, no server, no logs. You can verify in your browser DevTools → Network tab.

What if my PDF cannot be compressed to 400KB?

If the PDF contains many high-resolution images or complex graphics, 400KB may not be reachable while keeping it readable. The tool returns the smallest achievable size and reports the actual result so you can decide whether to retry.

Does this tool add a watermark?

No watermark, ever. ExactPDF is 100% free with no signup. Output PDFs contain the same content as the input — just smaller.

Does this work offline?

Yes. Once the page loads, you can compress PDFs without an internet connection — all processing runs locally via WebAssembly.

Compress PDF to 400KB

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Compress PDF to 400KB

Set a strict target size and keep the best readable result. 100% private, no upload.

🔒 Files never leave your device

Choose target size

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Target: 400 KB

Other exact-size pages

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Target: 400 KB. Files stay on this device.

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Max file size: 150MB

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