“Sign this PDF” can mean two very different things. Most of the time it means putting your signature on the page, the electronic equivalent of pen on paper. Sometimes, usually in business, government or regulated work, it means a digital signature: a cryptographic seal made with a certificate that proves who signed and shows whether the file changed afterwards.
TokPDF has a tool for each. This guide explains how to use both, what each actually proves, and the general legal points worth knowing. It is practical guidance, not legal advice.
Which kind of signature do you need?
If someone sent you a lease, an offer letter or a permission slip and asked you to sign and return it, a visible signature is almost always what they expect. If a portal, a tender or an e-invoicing system asks for a signature made with a certificate, or mentions PAdES, PKCS#7 or a qualified signature, you need a digital signature and the right certificate.
| Visible signature (Sign PDF) | Digital signature (Digital Signature) | |
|---|---|---|
| What you add | A drawn, typed or image signature on the page | A cryptographic signature using your certificate, optionally with a visible stamp |
| What it proves | That someone placed this mark; on its own, very little | Which certificate signed, and whether the file changed after signing |
| What you need | Nothing | A certificate file (.pfx, .p12 or .pem) and its password |
| Typical use | Everyday forms, letters, simple contracts | Official filings, B2B contracts, documents that must be tamper-evident |
Add a drawn, typed or image signature
Sign PDF opens your document in a viewer with a signature tool. It works in your browser, and neither the document nor your signature is uploaded.
Open Sign PDF and add your document.
Click the signature button in the toolbar and create a signature. Type your name and pick one of several handwriting-style fonts and a colour; Draw with a mouse, trackpad or finger, with an adjustable line thickness; or use Image to add a picture of your real signature.
Click the page where the signature should go, then drag its corners to resize it. Add as many signatures or initials as you need, on any page.
Click Save Signed PDF to download the signed copy.
Reusing a signature
Ticking the save option stores a signature in the viewer for next time, up to five. The Signature library keeps up to 20 more and lets you download one as a PNG or copy it to the clipboard. Both are kept in your browser’s local storage on this device only. They do not sync to other devices, and clearing your browser’s site data deletes them. On a shared or public computer, delete your saved signatures before you leave.
What a visible signature does not do
A visible signature is saved as a signature annotation: a vector drawing placed on top of the page. It is not merged into the page content. That has two consequences. Anyone with an annotation-capable editor could move or delete it, and nothing in the file records who added it or when.
For most everyday paperwork that is fine, because the evidence that you agreed is the email exchange and the returned document, not the pixels. If you want the signature fixed into the page so it cannot be dragged around, print the signed PDF to a new PDF with your system’s “Save as PDF” printer. If you need proof that the document was not altered, use a digital signature instead.
Sign with a digital certificate
Digital Signature signs a PDF with a certificate you already have. Certificates come from your employer, a national ID scheme or a commercial certificate authority, usually as a .pfx or .p12 file protected by a password. A .pem file also works if it contains both the certificate and the private key. TokPDF cannot issue certificates.
The signature uses the widely supported adbe.pkcs7.detached format with SHA-256. Your PDF and private key stay in the browser. The one network request the tool may make is to download your certificate’s issuer certificates from the address written inside the certificate, so it can build the chain; that request contains neither the document nor the key.
Open Digital Signature, add the PDF, then add your certificate file and enter its password. TokPDF shows the certificate’s owner and validity dates, and warns if it has expired.
Optionally fill in Reason, Location and Contact Info. They are stored in the signature and shown by PDF readers.
Tick Add visible signature if you want a stamp on the page. Position and size are in PDF points, with X and Y measured from the top-left corner of the page; an A4 page is about 595 × 842 points, so the default Y of 700 puts the stamp near the bottom. We recommend placing the visible stamp on the first page.
Sign and download. Open the result in Adobe Acrobat Reader and check the signature panel.
Limits of TokPDF’s digital signatures
- No trusted timestamp. The signing time comes from your computer’s clock, not from a timestamp authority. Workflows that require a timestamp server or long-term validation (LTV) data need a dedicated signing product.
- Not PAdES. Some EU e-government systems require the PAdES (ETSI.CAdES.detached) format. Check the requirements before you rely on TokPDF for those.
- Trust depends on the certificate. A self-signed or company-internal certificate will show as “validity unknown” in Acrobat until the recipient trusts it.
- Sign last. Any change after signing, including adding a visible signature or filling a form field, breaks the digital signature. Finish every other edit first.
Are electronic signatures legally binding?
In many countries, yes, for most everyday contracts. The United States recognises electronic signatures under the federal ESIGN Act and the state-level UETA. The EU’s eIDAS regulation defines three levels: simple, advanced and qualified electronic signatures. Only a qualified signature is automatically treated as equal to a handwritten one across the EU, and it requires a qualified certificate and signing device that TokPDF does not provide.
Every system has exceptions. Wills, some property and family-law documents, and anything that needs a notary or witness often require wet ink or a specific process. Validity also depends on proving who signed and that they intended to. When the stakes are high, ask the other party which signature they accept, or check with a lawyer in your jurisdiction.