Digital Signature Guide

Digital signature introduction has provided us with an opportunity to sign digital documents and send them off easier than printed ones but keeping them just as reliable. Signed with a digital signature PDF file is as legit as a paper signed by your hand.

What is a Digital Signature?

Quoting Wiki, “a digital signature is a mathematical scheme for verifying the authenticity of digital messages or documents”. But what is a digital signature for us users? It means that with a digital signature, one can protect their documents, indicate one’s approval and identity, and prevent changes after the document has been signed. It’s the same work that a regular signature is supposed to do.

Today’s electronic signature is an international thing, though standards in the US, in the EU, and in other regions may differ. Still, if you are using it with an internationally recognized media service, there should be no issues regardless of your current location.

Electronic signatures are easy to use and hard to hack (unless you are careless enough). Due to verification procedures necessary for receiving a certificate, they are just as reliable as traditional ones.

How Do Digital Signatures Work?

So, how do digital signatures work? The same way as paper ones: they indicate that you have read and approved the document, and it has not been modified after that. With digital keys and corresponding software it’s easy: if a document has been edited after being signed, it will not be recognized, and all the parties concerned may be notified about that.

It can be compared to two keys: a public one (added by sender) and a private one (added by the signing side). The two keys should both fit for a document to be opened. The signature is like the second key already in the keyhole, so it only takes the public key to open the e-document. But if it’s been modified, the private key will no longer fit, and the document will be impossible to open. If it can be opened, it means the signature is valid.

It takes a digital signatures certificate, though, for your signature to reflect your identity. How do digital certificates work? The certificate provider grants that the certificate you have received is indeed tied to your person or organization, requiring you to confirm your identity with your documents. This way, your digital identity bridges the gap between your physical identity and the signature on a PDF file.

Legality of Digital Signature

In the U.S., digital signatures are legit since 2000 when ESIGN (Electronic Signatures in Global and National Commerce) was issued. The UETA (Uniform Electronic Transactions Act) shapes electronic signature usage in most states (except New York and Illinois, whose laws have no significant differences except for more attention to security).

Laws in other countries (EU, Canada, India, China, South Africa, almost everywhere) also allow for digital signing documents. It’s rather surprising that some countries have not recognized it officially yet.

Last but not least: for your digital signature to be legit, it should be based on your digital signatures certificate that you can obtain through trusted third-party entities (like GlobalSign or IdenTrust). Some of them are paid, others free. Certificates are usually valid for a limited period of time, after which you have to renew them. Even if you opt for a commercial certificate that takes money, you will benefit from it by saving more time and expenses on stationery and equipment, let alone snail mail.

Why Use Digital Signature

First of all, it saves time. After getting a digital signature, PDF files can be shared immediately, and the signature will confirm your approval and your identity. You can use signature apps and services on your desktop, laptop, phone, or tablet, so you don’t need a special location for doing this.

Digital signing documents also lets you save on stationery. No need to have a printer and a pen, to waste paper, to use a scanner (okay, you have it in your phone now, but nevertheless). Without it all, processing documents will take much less time.

It prevents losing documents: as you receive a document that requires your signature, you are usually notified about it. You can even sign and send it immediately, so the sender does not even close the window as they see it returned. You save all the copies of the documents you sign, thus reducing risk if losing them (especially if you store them in a cloud).

The Different Types of Digital Signatures

Basically, there are two types of digital signatures:

  • Simple electronic signature (SES).
When you print a document, sign it by hand, scan and resend it – that’s an SES. When you add a signature line at the end of your emails, that’s also an SES. Signing a document manually with a stylus and a touchscreen is also a sort of SES. Convenient as it is, it cannot be taken seriously due to no digital protection at all. In short, the receiver cannot be sure that the signature proves the signatory’s identity. Whoever could have added that line or moved the stylus over the touchscreen.

  • Advanced (or qualified) electronic signature (AES/QES).
Not to be confused with Advanced Encryption Standard! This type of signature has all to be linked to the signatory. The signatory is the only person in control of the signature. The signed document does not remain readable if edited after signing.

Though American law does not define qualified signature, the regulations that require a certificate to link an advanced signature to the signatory are the same that in Europe where it’s defined officially.

Creating a Digital Signature in PDFLiner

While all the basic theory may sound too sophisticated, the actual way to digitally sign documents is a lot simpler. To add a signature with PDFLiner, you must do the following:

1. Enter the signature page and authorize with your email, Google, or Facebook. This is necessary, because your future signature needs to be linked to your other credentials to do its job of confirming your identity.
2. Click on the “Upload Document” button to select the PDF to digitally sign.
3. Click the “Sign” icon (with a fountain pen head) to start signing.
4. Enter your name for the service to generate a signature that looks handwritten.
5. Move the signature where you want it and click there to place it. The actual place does not matter, but you might want it at the bottom of your document.
6. Edit it (if necessary) with buttons that appear near your signature as it’s placed.
7. Confirm by pressing OK.
8. Click “Done” in the upper right corner.

Now you can share, print, save (as PDF or JPG), or directly email your document. By the way, if you continue using PDFLiner, your digital signatures, PDF files, and settings (like contacts to share documents) will be stored in the cloud.


What is digital signature in simple words?
It’s a fragment of code indicating that you have read and approved the document (agreement, notification, whatever). Due to the double key system of digital signature verification, the document can be processed by other parties only if it remained intact after signing.
How do I create a digital signature?
You can use online services (like ours) for that, or turn to built-in signing features of Adobe Acrobat Reader or Microsoft Word. Developers like this also help with purchasing certificates. Depending on how often you need this, you can purchase a certificate for unlimited use or subscribe to a plan that fits your needs.
What is the difference between a digital signature and an electronic signature?
A digital signature implies some digital protection. An electronic signature may be just a piece of text or graphics added to the body of a message or a document. In fact, a digital signature is a protected sort of electronic signature (but not vice versa).
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