How to sign a PDF electronically

The short answer

You can sign a PDF for free using built-in tools on your Mac, Windows PC, iPhone, or Android phone — no extra software needed.

How to sign a PDF on Mac

Open the PDF in Preview (the default PDF viewer), then:

  1. Click the Markup toolbar button (it looks like a pen tip)
  2. Click the Signature button
  3. Choose Create Signature — you can draw with your trackpad, use your iPhone, or hold a signed paper up to your camera
  4. Once saved, click your signature and drag it onto the document
  5. Resize and position it, then save the file

Your signature is stored in Preview, so you only need to create it once.

How to sign a PDF on Windows

Windows doesn’t have a built-in signing tool, but you can use the free version of Adobe Acrobat Reader:

  1. Open the PDF in Acrobat Reader
  2. Click Fill & Sign in the left panel
  3. Click Add Signature, then type, draw, or upload an image of your signature
  4. Click your signature to place it on the document
  5. Save the file

How to sign a PDF on iPhone or iPad

  1. Open the PDF in the Files app
  2. Tap the Markup button (pen icon) at the top right
  3. Tap the + button, then select Signature
  4. Draw your signature with your finger and tap Done
  5. Drag and resize the signature where you need it

How to sign a PDF on Android

Android doesn’t include a built-in PDF signing tool. Your best options:

  • Google Drive — open the PDF, tap Fill out form if the option appears
  • Adobe Acrobat Reader (free) — works the same way as the desktop version

Is an electronic signature legally valid?

In most cases, yes. Electronic signatures are legally recognized in the US, EU, and most countries for everyday documents like contracts, agreements, and forms.

However, some documents still require a notarized or wet ink signature — things like wills, certain real estate deeds, or court filings. When in doubt, check with whoever is requesting the signature.