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Scanning a handwritten signature, “cutting it out” as a PNG, and pasting it into a PDF document is one of the most common practices in B2B business. Although it seems fast and practical, from a legal standpoint such a signature image provides almost no protection.
If a dispute arises, a court treats a scanned signature on a PDF the same as any other image inserted into the document — anyone could have copied and pasted it without the owner’s knowledge.
| Feature | Scanned Signature/ Picture (SES) | Qualified Electronic Signature (QES) |
| Identity verification | None. There is no proof of who actually pasted the image into the PDF. | Complete. The signer’s identity has been verified by an official certification authority (ZertES / eIDAS). |
| Protection against alterations | None. The document can be altered without a trace after the image has been placed. | Kriptografska. Svaka izmjena teksta nakon potpisivanja automatski poništava potpis. |
| Legal equivalence | Not equivalent to a handwritten signature. | 100% legally equivalent to a handwritten signature on paper. |
| Burden of proof | You must prove in court who pasted the image into the document and when. | Teret dokazivanja je na strani koja osporava potpis — zakonski se pretpostavlja valjanost. |
Main risks of using scanned signatures in business
- Contract invalidation in the event of a dispute: If the other party decides to dispute their contractual obligation, they can simply claim they did not paste the signature image themselves. Without QES, the burden of proof falls on you, which is in practice almost impossible to prove.
- Rejection in public procurement and before state authorities: Regulations and legal frameworks (such as Switzerland’s DigiLex or EU public procurement law) explicitly reject bids and contracts signed with a plain scanned signature image.
- Loss of document integrity: When you send a PDF with a pasted-in signature image, the other party can alter the amount, deadlines, or terms in the document while your signature image remains unchanged at the bottom. With QES this is technically impossible, because the signature is cryptographically bound to the content.
When is QES necessary?
A simple e-signature or a scanned image may suffice for non-binding working notes or internal confirmations of receipt. However, QES becomes mandatory and unavoidable in the following situations:
- Public procurement contracts and tender documentation
- High-value B2B contracts or long-term partnership agreements
- Službena komunikacija sa sudovima, općinama i javnim tijelima
- Official communication with courts, municipalities, and public authorities
A signature image in a PDF provides only an illusion of security. By switching to QES, you ensure that every signed document has full legal validity, regardless of whether you’re signing a contract with a client next door or in Switzerland.
Try fast and simple document signing with QES certificates through our application:
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