Digital signatures have gradually replaced physical signatures in professional settings. A digitally signed PDF provides authentication, integrity, and non-repudiation — qualities impossible to guarantee with a scanned handwritten signature.

Types of electronic signatures

  • Simple Electronic Signature (SES): A signature image or checkbox — no strong legal value, but accepted for internal documents
  • Advanced Electronic Signature (AES): Cryptographically linked to the signer, detects subsequent changes — accepted in the EU for most contracts
  • Qualified Electronic Signature (QES): The legal equivalent of a handwritten signature in the EU — requires a digital certificate from an accredited authority

Free tools for PDF signing

Adobe Acrobat Reader (free) allows adding simple signatures: drawn, typed, or from an image. DocuSign, SignNow, and HelloSign offer limited free plans for advanced signatures. LibreOffice supports local digital certificates for free.

How to add a signature in Adobe Reader for free

Open PDF in Adobe Reader → "Fill & Sign" or "Tools" → "Certificates" → "Digitally Sign" → draw the signature zone → choose your certificate or create a simple signature. Save the signed document as a new PDF.

Legal validity in the EU

The EU eIDAS Regulation recognizes advanced and qualified electronic signatures as equivalent to handwritten signatures for commercial contracts. Check with a legal expert for requirements specific to your industry and jurisdiction.

💡 DocInspector Tip: DocInspector verifies existing digital signatures in your PDFs and shows whether the document was modified after signing.

Frequently asked questions

Does a photo of my signature have legal value?

No — a signature image provides no guarantee of authenticity or integrity. It can easily be copied and pasted into any document.

How do I verify if a digital signature in a PDF is authentic?

Adobe Reader automatically displays signature status: valid (green), unknown, or invalid (red). A valid signature confirms the author and that the document hasn't been modified.

Conclusion

Digital signatures are essential for modern professional documents. Choose the type matching your required security level and use verification tools to ensure received signatures are authentic.