How to sign a PDF online — securely and free (2026).
What an electronic signature is, whether it is legally valid, how to sign a PDF with mouse or finger in seconds, and when you need a "real" digital certificate.
In 2026, nobody prints a PDF just to sign it, scan it and send it back. That is a waste of time and paper. There are three ways to sign a PDF online — from the simplest to the most legally robust.
1. Signature image drawn with mouse or finger
Simplest solution. You open a PDF, draw your signature in the browser (mouse or finger on phone), and that image gets embedded in the PDF at your chosen position. Our tool does exactly this — all in the browser, the file never leaves your device.
2. Scanned image of your hand-written signature
If you want the signature to look more like your real one (not a browser-drawn doodle), do this once in your life:
- Sign with a black marker on white paper.
- Take a phone photo (or scan).
- In Gallery erase the background or make it pure white.
- Save as .png or .jpg.
You can then embed that image into every PDF you need to sign. Our tool also supports this scenario — instead of drawing, upload your signature image.
3. Legal digital signature (eIDAS, X.509 certificates)
A signature image, however much it looks like your hand-written one, is NOT a legal digital signature. A legal digital signature in the EU (including Montenegro which honours eIDAS) requires:
- A certificate issued by an authorised provider.
- A smart card or USB token (where the certificate is stored).
- Specialised software (Adobe Acrobat, JSign, e-government clients).
A legal digital signature applies to: contracts worth more than €5,000, submissions to government bodies, VAT and other tax filings. For everything else (internal contracts, sending to clients, personal correspondence) — a signature image is perfectly enough.
Frequently asked questions
Can a signature image be "copied" from one PDF to another?
Technically yes — someone with a skilled PDF editor can extract your signature image and move it to another document. That is why a signature image is not for the most important contracts. For routine documents (mail acceptance, consents, internal memos) — perfectly fine.
Can a signed PDF still be edited afterwards?
Yes, with a regular signature (image) the PDF can still be edited. If you want to "lock" a signed PDF — send us a request through the contact form, we plan to add a tool for that.