How to Sign a PDF Document Online: 2026 Guide

You've received a contract in PDF format and need to sign it without printing, scanning, or mailing? Good news: electronically signing a PDF is now as simple as sending an email, at zero cost in most cases. The trick is choosing 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 eIDAS-compliant solutions, their limitations, and how to sign your first PDF in two minutes flat.

The 3 Methods for Signing a PDF (and Their Limitations)

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

Method 2: Adobe Acrobat Reader (Fill & Sign). Convenient for capturing your own handwritten signature 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 recognized 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 editor, servers hosted in France, GDPR compliant). Create your account at certyneo.com/signup — no credit card required, email verification in 30 seconds.

Step 2: Upload Your PDF

From your dashboard, click 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 combined into a single envelope signed at once by the recipient.

Step 3: Place the Signature Fields

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

Step 4: Add the Signer

Enter the name and email of the person who needs to sign. For a high-stakes contract (employment contract, lease, important NDA), activate AES mode with OTP SMS: the signer will receive a unique code on their phone before they can validate, which strengthens identification and proof value. For a low-stakes document (simple attestation), SES mode via 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 in 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 that is compliant includes several elements: a digital certificate attached to the document (visible via Adobe Reader, Signatures tab), a SHA-256 cryptographic fingerprint that changes with any byte modification, a certified timestamp (TSA compliant RFC 3161), and an audit document listing each step. In case of inspection or dispute, these elements constitute your proof — much stronger than an image pasted into Word.

How Much Does It Cost?

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

Ready to Sign Your First PDF?

Create your free account at certyneo.com/signup and send your first envelope in less than 3 minutes. To learn more, check out our pillar guide on electronic signatures (/guide/signature-electronique) which details SES, AES and QES levels, or our article on the comparative legal value of electronic vs. handwritten signatures.