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How to sign a PDF in your browser (free)

Add a real digital signature — not just a picture of one — with a certificate generated on your device. No upload, no account: the file never leaves your browser.

1. Open the PDF

Open your document in the editor (or start from the Sign PDF page, which jumps straight to the signing dialog once you pick a file). Everything runs locally.

2. Open the signing dialog

Go to Document → Sign…. Enter the signer name (required) and an optional reason, such as "I approve this document".

3. Sign & download

Click Sign & download. The editor generates a fresh self-signed certificate (RSA-2048, SHA-256) entirely in your browser, signs the document with it, and downloads a copy named yourfile-signed.pdf. The document you have open stays the editable original.

Honest caveat: a self-signed certificate is cryptographically valid — it proves the file hasn't been altered since signing — but there is no certificate authority behind it, so other viewers (Adobe Acrobat, for example) will show it as untrusted or "validity unknown". That's expected. For legally trusted signatures you need a certificate issued by a CA or a qualified signing service.

4. Verify signatures in a PDF

When you open a PDF that already contains digital signatures, a signature badge appears in the top bar. Click it to review each signature: who signed, the reason and date, whether the document integrity check passes (the signed bytes are unmodified), whether the signature is authentic for its embedded certificate, and whether it covers the whole file or the file was changed after signing. Note that this verifies the cryptography — it does not check certificate trust chains, revocation, or timestamps.

5. Edit a signed PDF without breaking the signature

If you need to make changes to an already-signed document, use Save (keep signed revision) instead of a normal save. It appends your changes as an incremental update after the original bytes, so the earlier signed revision stays cryptographically valid.

Tip: if you just want a handwritten-style signature mark on the page (no cryptography), use the freehand Draw tool or stamp an image of your signature — see How to edit a PDF. To lock the file with a password instead, use Protect PDF.

Sign a PDF now →

More guides: Fill out a PDF form · Edit a PDF · Redact a PDF