How to sign a PDF online
Sign PDF offers three kinds of signature with very different purposes. A visual signature places your drawn signature or typed name on the page, just like signing by hand. A certificate signature uses your own P12/PFX digital certificate to sign the file cryptographically. And the Naiara integrity seal marks the PDF so that any later change can be detected.
It is worth knowing what each one does before you send a document, because they do not carry the same weight.
Step by step
- Upload your PDF and choose the signature type.
- Visual signature: draw with your finger or mouse and click use this signature, or type your name; then drag on the page to place it.
- Certificate: add your P12/PFX file, enter its password and, optionally, a reason for signing.
- Naiara seal: sign in with your free account and apply the seal to one PDF.
- Process and download the signed document.
What each signature is worth
A visual signature is only a mark on the page. It is fine for informal documents, internal approvals or when the recipient simply asks for 'the signed PDF', but it does not prove who signed. A signature with your P12/PFX certificate is backed by that certificate: if it was issued by a recognised provider, such as the personal certificates many people use for government services, the reader will identify you and confirm the document has not changed since signing. None of the options adds a qualified timestamp.
The Naiara integrity seal uses Naiara's own self-signed certificate. It detects later changes to the PDF, but it does not verify your identity or the content, it is not a qualified signature, and the date comes from the server. Many viewers will show it as untrusted because the certificate is not on their trust lists; you can download the public certificate and check its SHA-256 fingerprint from the tool.
When you need something else
If a process requires a qualified or advanced electronic signature (for example under eIDAS), or a timestamp from a trusted provider, neither the Naiara seal nor a visual signature will do; you need your own certificate or a dedicated e-signature service. If in doubt, ask the organisation which signature types it accepts.
The Naiara seal works on one PDF per operation and rejects encrypted files and PDFs that already contain form fields or digital signatures, so it never invalidates them by rewriting the file. Always sign last: any later change, even compression, breaks verification of a digital signature.
Frequently asked questions
- Is a drawn signature legally binding?
- It is a visual mark and does not by itself prove who signed. Where an electronic signature is required, use your digital certificate.
- Can I sign with my digital certificate?
- Yes, if you have it exported as a P12 or PFX file. You will need its password.
- What is the Naiara integrity seal?
- A signature made with a self-signed Naiara certificate that lets anyone detect if the PDF changes afterwards. It does not prove your identity and is not a qualified signature.
- Why does my PDF reader say the signature is untrusted?
- With the Naiara seal that is expected: the certificate is self-signed and not on readers' trust lists. The document's integrity can still be checked.
- Do I need an account to sign?
- Only for the Naiara seal, which requires signing in with a free account. Visual and certificate signatures do not.