Is a Pasted Signature Image in a PDF Valid? How It Differs from a Real E-Signature (2026)

Pasting a signature image into a PDF is technically doable, but it is not an "electronic signature" within the meaning of Thai law, because it is merely an image that anyone can copy into another document, with no identity verification and no timestamp showing who actually placed it. That is different from an electronic signature under Section 9 of the Electronic Transactions Act B.E. 2544 (2001), which must reliably identify the signer and show their intent. A pasted signature image therefore carries far less legal weight, especially when a dispute arises.

If you have been saving your own signature as a PNG file and pasting it into documents all along, this article is written specifically for you. Not to tell you the method is wrong, but to explain clearly how it differs from an electronic signature, and when each is appropriate.

TL;DR: Pasting a signature image into a PDF is technically doable, but it is not an electronic signature in the legal sense, because it is an image file that can be copied and reused, with no identity verification or timestamp attached. That is different from an electronic signing system that can verify identity under Section 9.

What you should know

• A signature image pasted into a PDF is just an image file, not an electronic signature in the legal sense.
• The main risk is the image file being copied and used in other documents without the owner knowing.
• Section 9 sets out 3 elements: the signer can be identified, the method is appropriate to the circumstances, and intent can be shown.
• A hand-drawn signature still works exactly as before; the difference is the identity verification behind it, not how it looks.

Is a pasted signature image in a PDF usable?

Usable in a technical sense, but legally it is not equivalent to an electronic signature. Saving your signature as a file once and pasting it repeatedly into documents is extremely widespread, because it is fast, needs no special tools, and carries over the old habit of printing a document, signing by hand, and scanning it back into the computer.

For very low-risk documents, such as internal team sign-offs with no serious legal consequences, this method may be adequate in practice. But for legally binding contracts, such as leases, sale agreements, or medical consent forms, the risk of using an image in place of a real electronic signature starts to become significant.

How does a signature image differ from an electronic signature?

An image does not prove who actually placed it, when, or whether the document was modified afterward, while an electronic signature under Section 9 does all three. That is the core difference to understand.

Section 9 of the Electronic Transactions Act requires that, to count as a legal signature, the method must be able to identify the signer, must be appropriate to the purpose for which the electronic data was created or sent, and must show that the person accepted the content of that electronic data.

If you are also using AI to draft contracts, be aware that combining the two weaknesses, unverified content plus an image-based signature with no identity verification, doubles the risk. Read more on AI drafting risks at Can AI draft a contract? What the risks are

What are the risks of a signature image or scanned signature?

The main risk is reuse. A signature image is an ordinary image file, and it can be copied and pasted into other documents exactly like any other image. This is the point most people never think about until a real problem occurs.

Here is a plausible scenario: a signature image you once sent by email or LINE gets saved on the recipient's device and placed into another document the signature's owner has never seen. When that happens, the owner has almost no way to prove they did not actually sign that document, because there is no trace of where or when the signature was created.

This is not meant to alarm you. In practice, plenty of low-risk documents never run into any problem from a pasted signature. But the higher a document's value or dispute risk, the stronger the case for a signing method that verifies identity instead of relying on an image alone.

What makes an electronic signature legally valid (Section 9)?

The 3 elements that make an electronic signature valid under Section 9 are: the signer can be identified, the method is appropriate to the circumstances, and intent can be shown reliably. A good electronic signing system has to satisfy all three at once, not just one.

1. Identifying the signer. Done through identity verification on a channel separate from the document itself, such as an OTP code sent specifically to the signer's email address or phone number.
2. A method appropriate to the circumstances. The strictness of identity verification should match the value and risk of the transaction; a high-value contract deserves tighter verification than a routine document.
3. Showing intent reliably. Done through detailed timestamps and a record of the signing steps (an audit trail) showing that the signer actually saw that document and confirmed it themselves.

A system that combines all three in one flow, open the document link, verify identity with an OTP, then sign by hand on the screen, produces something that looks exactly like a traditional signature, but with an identity-verification and timestamping layer behind it that a plain pasted image does not have.

Read next: The difference between electronic signatures and digital signatures

Frequently asked questions

Is a scanned signature in Word the same as in a PDF?

The same. Both are just image files pasted into a document, and neither is an electronic signature in the legal sense, whatever the file type.

I've pasted signature images for years without a problem. Do I need to change?

The risk only becomes visible when a dispute arises. The higher the document's value or likelihood of disagreement, the sooner you should switch to a system that can verify identity.

Can someone really steal a signature image and use it?

Technically yes, because a signature image can be copied exactly like any other image file. There is no built-in mechanism preventing reuse.

Does an electronic signature still look like a hand-drawn one?

Yes. Most systems, including Jabmue, let you draw your signature with a finger or mouse just as before. The difference is the identity verification and record-keeping behind it, not what the signature looks like on screen.

Do documents I've already signed with a pasted image need re-signing?

It depends on the document's importance. High-value documents or those with real dispute risk are worth re-signing through a system that verifies identity; low-risk documents may not need it.

Conclusion

A signature image pasted into a PDF is not an electronic signature within the meaning of the law. The main risk is not how it looks, but that it can be reused like any ordinary image file. What makes a signature legally binding is the identity verification and timestamping behind it, not the appearance of the signature on the screen.

If you want to keep signing with a hand-drawn signature that looks exactly the same, but with OTP identity verification and a full audit trail that meets Section 9, try it free and see the difference yourself.