What a digital signature is and why you need one

A digital signature is an electronic way to sign documents that proves who you are and shows the document hasn't been changed since you signed it. It works differently from typing your name or using a stylus to draw a signature — a digital signature uses encryption technology to create a unique code tied to your identity.

You'll encounter digital signatures when signing contracts, tax forms, loan documents, or agreements online. They're legally binding in most countries, including the United States under the Electronic Signatures in Global and National Commerce Act (E-SIGN). Banks, government agencies, and businesses accept them as proof of your consent.

The main benefit is speed: you can sign documents from your computer or phone without printing, scanning, or mailing anything. The security benefit is that a digital signature creates a record of when you signed and prevents anyone from altering the document after you've signed it.

Key Takeaways

  • Digital signatures use encryption to prove your identity and protect documents from being changed after you sign them.
  • You can create a simple digital signature using free tools like DocuSign, Adobe Acrobat Reader, or your email provider, or use your operating system's built-in options.
  • A basic digital signature for personal use takes minutes to set up, while legally certified signatures for business require verification through a third-party provider.
  • Different documents and situations require different signature types — casual PDFs need only a basic signature, while contracts and financial documents may need certified signatures.
  • Once you create a digital signature, you can reuse it on multiple documents, and most programs let you store it for quick access.

The difference between basic and certified digital signatures

A basic digital signature is what most people use for everyday documents. You draw your signature on a touchpad or trackpad, type your name, or upload an image of your handwritten signature. These are quick to create and work fine for contracts between people who know each other, internal company documents, or any situation where both parties trust each other.

A certified digital signature (also called a may have access to signature) involves a third-party verification service that confirms your identity before issuing you a digital certificate. This certificate contains encryption keys that prove you are who you say you are. Certified signatures are required for legal documents, government filings, financial transactions, and situations where you're signing with someone who doesn't know you.

For most personal use — signing a PDF, approving a document at work, or signing a contract with a friend — a basic signature is enough. If you're signing something for a bank, government agency, or a formal business contract with a stranger, you'll need a certified signature from a provider like DigiCert, Sectigo, or your country's official certificate authority.

Creating a basic digital signature on Windows or Mac

Both Windows and Mac have built-in tools for basic digital signatures. On a Mac, open any PDF in Preview, click the Markup toolbar button (it looks like a pen in a circle), then select Signature. You can draw your signature with your trackpad, use your iPhone camera to photograph a handwritten signature, or type your name. Once created, your signature saves and you can use it on future documents.

On Windows, open a PDF in Microsoft Edge or Adobe Acrobat Reader. In Acrobat Reader, click the Fill & Sign tool on the right side, then click Sign. You can draw your signature, type your name, or upload an image. Windows also lets you create a signature in Microsoft Word by going to Insert > Signature Line, though this creates a placeholder rather than an actual signature.

These built-in signatures are basic and not encrypted, so they work for documents between people who trust each other but won't hold up for formal legal or financial documents. They're free and take less than a minute to create.

Using DocuSign or Adobe to sign documents

DocuSign and Adobe Acrobat both offer free tiers that let you create and store a digital signature. With DocuSign, you sign up for a free account, create your signature by drawing, typing, or uploading an image, and then you can sign documents sent to you or upload your own. DocuSign stores your signature and remembers where you usually sign on different document types, so the second time you sign something similar, it fills in automatically.

Adobe Acrobat Reader (the free version) lets you sign PDFs without creating an account. Open any PDF, click Fill & Sign, then click Sign, and create your signature the same way. If you want to store your signature for reuse, you'll need an Adobe account, which is free. Adobe also lets you request signatures from others — you upload a document, add signature fields, and send it to someone else to sign.

Both services work on Windows, Mac, iPhone, and Android. The free versions cover most personal signing needs. If you need to send documents to multiple people for signature or need certified signatures, both offer paid plans, though the free tier is enough for signing documents sent to you.

Getting a certified digital signature for legal documents

To get a certified digital signature, you'll work with a Certificate Authority — a company authorized to verify your identity and issue digital certificates. Common providers in the United States include DigiCert, Sectigo, GlobalSign, and Entrust. Your bank or employer may also offer certified signatures through their own systems.

The process typically involves providing government-issued ID, proof of address, and sometimes a video call where you verify your identity in real time. The provider then issues you a digital certificate that contains encryption keys unique to you. This certificate proves to anyone who receives a document you signed that you are who you claim to be and that the document hasn't been altered.

Certified signatures cost money — usually between $50 and $300 per year depending on the provider and how many documents you plan to sign. The process takes a few days to a week because the provider must verify your identity. Once you have the certificate, you can use it in Adobe Acrobat Pro, Microsoft Office, or specialized signing software to sign documents with a certified signature that holds up in court and with government agencies.

Signing documents on your phone or tablet

Most phones and tablets let you sign documents using apps like DocuSign, Adobe Fill & Sign, HelloSign, or Notarize. On an iPhone or iPad, you can also sign PDFs directly in the Mail app or in Apple Books by using the Markup tool. Open the document, tap Markup, draw your signature with your finger, and it saves to that document.

For Android, Google Drive lets you open PDFs and use the drawing tool to sign, though it's less polished than Apple's version. DocuSign and Adobe apps work the same way on Android as they do on iPhone — you create your signature once and reuse it across documents.

Signing on a phone is slower than on a computer if you're using a stylus or your finger to draw, but it's faster if you're already on your phone and need to sign something immediately. Most services sync your signature across devices, so you can create it on your computer and use it on your phone, or vice versa.

Storing and reusing your digital signature safely

Once you create a digital signature, the program or service stores it so you don't have to recreate it each time. DocuSign, Adobe, and most email services save your signature in your account. If you use a certified signature, your digital certificate is stored on your computer or in a secure cloud vault provided by your Certificate Authority.

For basic signatures, there's little security risk — your signature is just an image or drawing. For certified signatures, protect your private key the same way you'd protect a password: don't share it, don't email it, and don't store it on a shared computer. If you lose access to your certified signature, you'll need to contact your Certificate Authority to revoke the old certificate and issue a new one.

Most services let you delete or update your signature at any time. If your signature changes — you change your legal name, for example — you can create a new one and the old one will no longer be used for new documents. Old documents you've already signed remain signed with the old signature and can't be changed.

Frequently Asked Questions

Is a digital signature legally binding?

Yes, in the United States and most countries, digital signatures are legally binding under the E-SIGN Act and similar laws. However, the document itself must be one that can legally be signed electronically — some documents like wills, powers of attorney, and certain real estate contracts still require handwritten signatures in some states. Check with your state or the other party before signing something important digitally.

Can someone forge my digital signature?

A basic digital signature (a drawing or image) can be copied if someone has access to your files, but certified signatures cannot be forged because they're encrypted and tied to your identity through a Certificate Authority. If you use a certified signature, forging it would require stealing your private key, which is protected like a password. For basic signatures, only share signed documents with people you trust.

What if I need to sign something but don't have a printer?

You don't need a printer at all for digital signatures. Open the document on your computer or phone, use any of the free tools mentioned here to add your signature, and send the signed PDF back. The other person receives a document with your signature already on it — no printing or scanning required.

Can I use the same digital signature on every document?

Yes, you can reuse the same basic digital signature on as many documents as you want. Most services store it specifically so you don't have to recreate it. For certified signatures, you use the same certificate for all documents, though the signature itself changes slightly each time because it includes the date and time you signed.

What happens if I sign a document by mistake?

Once you sign a document, you can't unsign it or change it without the signature becoming invalid. If you sign something by mistake, you'll need to contact the other party and ask them to send you an unsigned version, or ask them to delete the signed version and start over. This is why it's important to read documents carefully before signing them digitally.