How to Sign a PDF Document Online: Guide 2026

You have received a contract in PDF format and you need to sign it without printing, without scanning, without postal mail? Good news: electronically signing a PDF is now as simple as sending an email, at zero cost in most cases. However, you need to choose the right method: some popular options (scanned image, Adobe Fill & Sign) have virtually no legal value. In this guide, we present you with the real solutions compliant with eIDAS, their limitations, and how to sign your first PDF in two minutes flat.

The 3 Methods to Sign a PDF (and Their Limitations)

Method 1: Paste a scanned signature image. This is the most widespread solution but the least secure. Legally, this does not constitute an electronic signature under Article 1367 of the Civil Code: no identification of the signer, no integrity guarantee. In case of dispute, the evidence is very weak.

Method 2: Adobe Acrobat Reader (Fill & Sign). Convenient for your own handwritten signature captured with a mouse, but again: no digital certificate, no timestamp, no audit trail. Legal value virtually identical to the scanned image.

Method 3: An eIDAS-compliant electronic signature platform (Certyneo, DocuSign, Yousign, etc.). This is the only method that produces a PDF with cryptographic signature, certified timestamp and complete audit trail. Legal value recognised throughout Europe.

Step 1: Choose Your Platform

Most platforms offer a free plan sufficient for a few signatures per month. For this guide, we use Certyneo (free plan: 5 envelopes/month, French publisher, servers hosted in France, GDPR compliant). Create your account on certyneo.com/signup — no bank card required, email verification in 30 seconds.

Step 2: Upload Your PDF

From your dashboard, click on New Envelope, then drag and drop your PDF file (up to 25 MB). The document appears in the editor. You can upload multiple PDFs in succession: they will be grouped together in a single envelope signed at once by the recipient.

Step 3: Place the Signature Fields

Click on the Signature button, then drag the field to the location where the recipient must sign. Repeat for each page that requires a paraph (for example, a 10-page contract may have one paraph per page + one final signature). You can also add Date, Text, Checkbox fields for mandatory handwritten entries (read and approved, approved, etc.).

Step 4: Add the Signer

Enter the name and email address of the person who must sign. For a high-stakes contract (employment contract, lease, important NDA), activate AES mode with SMS OTP: the signer will receive a unique code on their phone before validation, which strengthens identification and proof value. For a low-stakes document (simple attestation), SES mode by email click is sufficient.

Step 5: Send and Track

Click Send. The recipient immediately receives an email with a personal link. They click, see the document full screen, sign with one click (or after entering their OTP). You receive a notification as soon as the signature is complete. The final signed PDF is downloadable from your dashboard, accompanied by an audit certificate (separate PDF) that timestamps each action: document opening, OTP validation, signature, IP address, user agent.

What a Compliant Signed PDF Contains

An electronically signed PDF in a compliant manner includes several elements: a digital certificate attached to the document (visible via Adobe Reader, Signatures tab), a SHA-256 cryptographic fingerprint that changes at the slightest byte modification, a certified timestamp (TSA compliant RFC 3161), and an audit document listing each step. In case of review or dispute, these elements constitute your proof — much stronger than an image pasted in Word.

How Much Does It Cost?

For an individual or a small business that signs fewer than 5 contracts per month, the free Certyneo plan (or other market players) is more than sufficient: €0 per month, all legal features included. Beyond that, paid plans start at around €10/month for intensive use (50 to 200 envelopes). See the /pricing page for details on Certyneo's plans.

Ready to Sign Your First PDF?

Create your free account on certyneo.com/signup and send your first envelope in less than 3 minutes. To go further, consult our pillar guide on electronic signature (/guide/electronic-signature) which details SES, AES and QES levels, or our article on the compared legal value of electronic signature vs handwritten.