The simplest way to sign a PDF is to add an image of your signature to the page: draw it with your finger or mouse, type your name in a handwriting-style font, or upload a photo of your signature, then place it on the signature line and save. That creates an electronic signature, which many organizations accept for everyday documents like leases, permission slips and service agreements. Some documents instead require a certificate-based digital signature, which is a different technology with stronger verification.
This guide explains the difference in plain language, walks through signing on Mac, Windows, iPhone and in the free Adobe Reader, and shows how to sign privately in your browser. It also covers the legal basics, with the caveat that rules vary by country and document type.
Electronic signature vs. digital signature
People use these terms interchangeably, but they describe different things.
Electronic signatures
An electronic signature is any electronic indication that a person agrees to a document. It can be:
- An image of a handwritten signature placed on a PDF.
- A typed name.
- A checkbox labeled "I agree" in an online form.
- A signature captured by an e-signing service along with an audit trail of emails, timestamps and IP addresses.
When you add your drawn or typed signature to a PDF yourself, the result is a visual mark on the page. It shows intent, but the PDF itself does not contain cryptographic proof of who added it or whether the document changed afterward.
Digital signatures
A digital signature, in the technical sense, uses public-key cryptography. The signer has a certificate, often issued by a trusted certificate authority or an organization, and the PDF viewer can check two things:
- Integrity: whether the document has changed since it was signed.
- Identity: which certificate was used, and whether that certificate is trusted.
When you open a digitally signed PDF in a viewer that supports it, you typically see a signature panel reporting whether the signature is valid. Setting up a certificate is more involved, and verification depends on the viewer trusting the certificate chain.
Which one do you need
For most personal and small-business paperwork, an electronic signature is what the other party expects. Certificate-based digital signatures are more common for government filings, certain regulated industries, and organizations that issue certificates to employees. If the document or the recipient specifies a signing method, follow those instructions.
A note on legal validity
This is general information, not legal advice.
In many jurisdictions, electronic signatures are legally recognized for a wide range of transactions. In the United States, the federal ESIGN Act and the Uniform Electronic Transactions Act, adopted by most states, give electronic signatures the same general standing as handwritten ones for many transactions. In the European Union, the eIDAS regulation defines simple, advanced, and qualified electronic signatures, with qualified signatures carrying special legal weight.
Common exceptions in many places include wills, certain family law documents, some real estate transactions and court documents, and notarized papers, which may require wet-ink signatures or specific procedures. Requirements change and vary, so check local rules or ask the requesting organization, and consult a lawyer for anything high stakes.
How to sign a PDF with built-in tools
Preview on a Mac
- Open the PDF in Preview.
- Click the Markup button (a pen tip icon) to show the markup toolbar.
- Click the Sign button.
- Create a signature using the trackpad, by signing on white paper and holding it up to the camera, or on a nearby iPhone or iPad if your devices support it.
- Select your signature to place it, then drag and resize it on the signature line.
- Save, or use File > Export as PDF to keep the original untouched.
Preview remembers your signatures for future documents.
iPhone and iPad
- Open the PDF in the Files app or from a Mail attachment.
- Tap the Markup button.
- Tap the + button and choose Add Signature.
- Sign with your finger, tap Done, then position and resize the signature.
- Tap Done to save.
Windows and Adobe Reader
Windows does not include a dedicated PDF signing feature, though Microsoft Edge's built-in PDF viewer offers drawing and text tools that some people use to add a signature. A more common free option is Adobe Reader's Fill & Sign feature:
- Open the PDF in Adobe Reader.
- Choose Fill & Sign from the tools.
- Choose Sign yourself, then Add signature.
- Type, draw or upload an image of your signature.
- Place it on the page and save.
Adobe also offers certificate-based signing in Reader for users who already have a digital ID, and paid services for sending documents out for signature.
How to sign a PDF in your browser
Our free Sign PDF tool works on any modern browser, including phones. The PDF is processed on your device and is never uploaded, which matters because signed documents often contain addresses, account numbers and other personal details.
- Open Sign PDF and add your document.
- Create your signature in one of three ways:
- Draw it with a mouse, trackpad, stylus or finger.
- Type your name and let the tool turn it into a signature image.
- Upload a photo or scan of your handwritten signature.
- Place the signature on the page, then drag and resize it to fit the line.
- Repeat on other pages if the document needs initials or multiple signatures.
- Download the signed PDF.
The result is an electronic signature: your signature is embedded into the page as an image. The tool does not apply a certificate-based digital signature.
Getting a clean uploaded signature
If you upload a photo of your signature:
- Sign with a dark pen on plain white paper.
- Photograph it in even light, straight on.
- Crop tightly around the signature before uploading.
- A PNG with a transparent background looks most natural on colored forms, but a well-lit JPG on white paper also works.
Before and after signing
Fill out the form first
If the document has form fields for your name, date and address, complete them with Fill PDF form before signing. For documents without fields, Add text to PDF lets you type anywhere on the page, such as next to "Date".
Flatten to lock things in place
A filled form can still be edited by anyone who opens it. Flatten PDF converts form values into regular page content so they cannot be changed casually. It is a good step before sending a completed form. Note that flattening does not create cryptographic protection; it simply removes the editable fields.
Protect sensitive signed documents
If you are emailing a signed agreement that contains personal information, consider adding an open password with Protect PDF and sharing the password through a separate channel.
Good signing habits
- Read the final version. Make sure you are signing the document you agreed to, not an earlier draft.
- Keep a copy. Save the signed PDF somewhere you can find it later.
- Be cautious with your signature image. Treat a saved signature file like a key. Avoid leaving it on shared computers or uploading it to services you do not trust.
- Watch for signature requests you did not expect. Phishing emails sometimes impersonate e-signing services. If in doubt, contact the sender through a known channel.
- Follow instructions from the recipient. If a bank, agency or employer asks for a specific signing method, use it.
Key takeaways
- Adding a drawn, typed or uploaded signature image to a PDF creates an electronic signature, suitable for many everyday documents.
- Certificate-based digital signatures add cryptographic proof of integrity and identity and are required in some contexts.
- In many jurisdictions electronic signatures are legally recognized, but exceptions exist; check local rules and the recipient's requirements.
- Preview, the iPhone Markup tools and Adobe Reader's Fill & Sign all offer free native signing.
- Our in-browser Sign PDF tool lets you draw, type or upload a signature and place it anywhere, without uploading the document.