Digital signatures: more than just an image
When adding a digital signature to a PDF for the first time, many people think: I'll just take a photo of my signature and insert it. That is technically possible, but whether it is legally sufficient depends on the intended use. In the EU, the eIDAS Regulation governs which type of electronic signature is recognized for which purposes.
This article explains the most important signature types, when each applies and how to easily and quickly add a digital signature to a PDF.
The three signature types under eIDAS
Simple Electronic Signature (SES)
The simplest form: a scanned signature image, a typed name, or a click on "I agree". No technical security features, no identity verification. Sufficient for informal agreements, internal documents or order confirmations, but not for legally binding contracts under many national laws.
Advanced Electronic Signature (AdES)
Here, the signature is uniquely linked to the signatory. It is created with data that only the signatory controls and is linked to the document so that any subsequent change would be detectable. Typical for signatures created via qualified services like DocuSign or similar platforms.
Qualified Electronic Signature (QES)
The highest level. Legally equivalent to a handwritten signature under EU law. Requires prior identity verification (video identification or in-person) and a qualified certificate. Necessary for notarially relevant processes, employment contracts in certain sectors or other legally regulated documents.
When is which signature sufficient?
For most everyday documents, NDAs, quotes, order confirmations, minutes, a simple or advanced electronic signature is perfectly sufficient. The parties simply need to agree that the signature is accepted.
Legally mandated written form requirements (e.g., for certain contract terminations, notarial acts) require a qualified electronic signature or paper.
How to add a digital signature to a PDF
With our sign PDF tool, a signature can be added directly in the browser. Several methods are available:
- Draw a signature with mouse or touchpad
- Upload a photo or scan of a handwritten signature
- Type a signature in cursive font
After adding the signature, its position can be freely placed anywhere in the document, the size adjusted, and the signed PDF downloaded.
Multiple people need to sign
When multiple parties need to sign a document, there are two approaches: either send the PDF to each signatory in turn (each adds their signature), or use a dedicated e-signature service with workflow functionality.
For smaller scenarios without complex workflows: sign the document, save it, forward it, done. Anyone wanting to compare the document before and after signing can use compare PDF.
Security and integrity of signed PDFs
For a signature to serve its purpose, the document must not have been changed after signing. Many PDF signatures therefore contain a cryptographic checksum, if the document is subsequently edited, the signature is marked as invalid.
Anyone wanting to additionally protect a signed document against unauthorized access can use protect PDF to add a password, preventing further changes while still allowing reading.
Conclusion
Digital signatures in PDFs are practically and legally fully sufficient for most everyday use cases. Anyone who understands the basic rules, which signature type suits which purpose, saves time, paper and postage. For everyday documents, a simple electronic signature is entirely adequate.