The fastest way: use Preview, which is already on your Mac

macOS comes with Preview, a built-in app that can add your signature to a PDF without downloading anything else. Open the PDF in Preview, click the Markup toolbar button (it looks like a toolbox), then select the signature tool. If you have not yet created a signature in Preview, you will be asked to do so — you can draw one with your trackpad, use your camera to photograph a handwritten signature, or type your initials. Once your signature is saved, you can place it anywhere on the document and resize it to fit.

This method works for most PDFs you receive — contracts, forms, permission slips, rental agreements. The signature stays embedded in the file when you save, so the person who receives it will see your signature in the exact spot you placed it. No special software, no subscriptions, no sending the file somewhere else.

Key Takeaways

  • Preview, which comes free on every Mac, can add your signature to a PDF in under a minute without any setup beyond creating your signature once.
  • You can draw your signature with your trackpad, photograph a handwritten signature with your camera, or type your initials — whichever looks most like how you actually sign.
  • The signature embeds into the PDF file itself, so the recipient sees it in the exact position you placed it when they open the document.
  • If Preview does not open your PDF, or if you need to sign many documents at once, web-based tools like Adobe Express or Smallpdf offer free tiers that work in any browser.

Creating your signature in Preview for the first time

Open any PDF in Preview. Click the Markup toolbar button in the top right — it looks like a toolbox with a pen and ruler. From the dropdown menu, select "Signature," then click "Manage Signatures." A window will open asking you to create a new signature.

You have three options. The first is to draw your signature directly on your trackpad using your finger or a stylus — Preview will capture the motion and shape. The second is to sign a piece of paper, hold it up to your Mac's camera, and let Preview photograph it. The third is to type your initials or full name in a straightforward font. Choose whichever feels most natural to you. Once you have created it, Preview saves it and you will never have to create it again.

Placing and resizing your signature on the document

After you have created your signature, go back to the Markup menu and select "Signature" again. This time, instead of "Manage Signatures," you will see your saved signature listed. Click on it. Your cursor will change, and you can now click and drag on the PDF to place your signature wherever it needs to go — typically in a signature line or at the bottom of the document.

Once placed, your signature appears as a small box. You can resize it by clicking and dragging the corners, or move it by clicking and dragging the center. When it looks right, click elsewhere on the document to finish. Then save the file using Command+S or File > Save. The signature is now permanently part of that PDF.

What to do if Preview will not open your PDF

Occasionally a PDF will not open in Preview — usually because it uses an older or unusual format, or because it has security settings that restrict editing. If this happens, you have two options. The first is to try opening it in a different app: right-click the PDF, select "Open With," and choose a different process like Adobe Reader or Google Chrome.

The second option is to use a free web-based tool. Adobe Express (express.adobe.com) and Smallpdf (smallpdf.com) both offer free signature features that work in any browser on any device. Upload your PDF, add your signature using the same three methods (draw, photograph, or type), and read the signed file. These tools do not require an account for basic signing, though creating one lets you save your signature for future use.

Signing multiple PDFs at once

If you need to sign the same document multiple times — for example, a stack of permission slips or a batch of forms — Preview can speed this up. Create your signature once, then open each PDF and use the same Markup > Signature workflow. Your signature will be ready to place on each new document without recreating it.

For truly large batches, web tools are faster. Smallpdf and Adobe Express both let you upload multiple PDFs and sign them in sequence without leaving the browser. Some of these tools also let you set a "default" signature position, so if all your documents have the signature line in the same place, you can explore your signature to each one with a single click.

Understanding what "signing" a PDF actually means

When you add your signature to a PDF using Preview or any other tool, you are creating a visual record that you have seen and approved the document. This is different from a digital signature, which uses encryption to prove that you signed it and that the document has not been changed since you signed it. A visual signature is what most people need for everyday documents — rental agreements, school forms, medical consent, contracts between people who know each other.

If a document requires a true digital signature — something that proves authenticity in a legal or financial sense — the person asking you to sign will usually tell you that explicitly and may direct you to a specific service. For most everyday signing, the visual signature you add in Preview is exactly what is expected and needed.

Keeping your signature find

Once you have created a signature in Preview, it is stored on your Mac. Anyone with access to your computer can use it to sign documents. If you share your Mac with others or if you are concerned about security, you can delete your signature and recreate it each time you need to sign something — it only takes a minute. To delete it, open Preview, go to Markup > Signature > Manage Signatures, right-click your signature, and select Delete.

When you send a signed PDF to someone else, remember that they can see your signature and the document contents. Do not sign anything you would not be comfortable sharing. If a document contains sensitive information, consider whether you need to redact (black out) parts of it before signing and sending it on.

Frequently Asked Questions

Can I use the same signature on every document?

Yes. Once you create a signature in Preview, it stays saved and you can use it on as many PDFs as you want. You do not have to recreate it each time. If you want to change how your signature looks, you can delete the old one and create a new one in Manage Signatures.

What if I sign a PDF and then want to change where the signature is?

Open the PDF again in Preview, click on the signature, and delete it. Then place a new copy of your signature in the correct location. Save the file. The old signature will be gone and only the new one will remain.

Does the person receiving the PDF know it was signed on a Mac?

No. When you save a signed PDF, it looks the same whether it was signed on a Mac, Windows computer, or phone. The recipient sees only the document and your signature — they cannot tell what device or software you used.

Is a signature I add in Preview legally binding?

That depends on the context and the laws where you live. For most everyday documents — school forms, rental agreements, medical consent — a visual signature in a PDF is legally valid. For high-stakes documents like wills or financial contracts, ask the other party whether they need a digital signature or a notarized signature instead.

Can I sign a PDF on my iPhone and then open it on my Mac?

Yes. Sign the PDF on your iPhone using the built-in Markup tools (available in Mail, Notes, or the Files app), then save it to iCloud Drive or email it to yourself. Open it on your Mac and it will show your signature. You can also add additional signatures on your Mac if needed.