How to Add Your Signature to a PDF: on Windows, Mac, iPhone and Android

Print the PDF, sign it, scan it back in: these days you almost never have to. Every device has a free way to put a signature straight into a PDF. Here are the ways for Windows, Mac, iPhone and Android. It looks best when you have your real signature as a transparent image once and reuse it everywhere.

Preparation: your signature as an image

All the apps below let you draw your signature with a mouse or finger. It rarely looks like your real signature, though. Better: sign once on paper, photograph it, remove the background and load the PNG as an image in each app.

Windows: with Adobe Acrobat Reader

Acrobat Reader is free, and Adobe lets you type, draw or upload an image of your signature with its Fill & Sign tool¹. Here is how:

1. Open the PDF in Acrobat Reader.
2. Choose the Fill & Sign tool.
3. Click Add signature. You can type your name, draw with the mouse or load an image. For your real signature, choose the image and select your PNG.
4. Confirm, drag the signature into place and resize it by the corners.
5. Save the file. Reader remembers the signature for next time.

Without Adobe, Windows can do it in the browser: Microsoft Edge opens PDFs and has a draw function. You can only draw with the mouse there, not insert an image.

Mac: with Preview

On a Mac you need no extra app. Preview can capture and save signatures²:

1. Open the PDF in Preview.
2. Click Show Markup Toolbar, then the Sign button.
3. Create a signature. Three ways: with your finger on the trackpad, with your iPhone or iPad, or with the camera. For the camera, hold your signature on white paper up to it and line it up with the blue line.
4. Click Sign again, choose the saved signature, drag it into place and resize it by the handles.
5. Save with File > Save.

The camera option already gives a decent result. In poor light or with a thin pen, though, it tends to lose fine strokes. If that happens: create a transparent PNG, open it in Preview, copy it and paste it into the PDF.

iPhone and iPad: with Markup

On the iPhone, signing is part of the Markup tools built into Files, Mail and Photos³:

1. Open the PDF in the Files app or as an attachment in Mail.
2. Tap the Markup icon (pen tip).
3. Tap the add button (plus) and choose Add Signature.
4. Sign with your finger or Apple Pencil and tap Done.
5. Move the signature into place, resize it, then tap Done again.

Hardly anyone signs with a finger the way they do on paper. To use your real signature on an iPhone, use the Acrobat app and load your PNG as an image.

Android: with the Acrobat app

Google Drive on Android can fill in PDF forms, but the Drive app has no signing function there⁴. The easiest free way is the Adobe Acrobat Reader app:

1. Open the PDF in the Acrobat app, for example via Open with from your email or downloads.
2. Tap Fill & Sign.
3. Draw your signature with your finger or choose an image from your gallery.
4. Place it, resize it, save and share.

Some Samsung devices also have their own PDF features, depending on model and version.

Common problems

• White box around the signature: you loaded a JPG or a photo without transparency. Use a PNG with a transparent background.
• The signature looks pixelated: the image was too small. For a PDF, 600 to 1,000 pixels wide is enough.
• The PDF cannot be edited: some PDFs are locked or already digitally signed. Then the only options are printing it or asking the sender for an editable version.
• The other side wants an original: then an inserted signature is not enough, see the next section.

Is an inserted signature legally binding?

In England and Wales, usually yes. Electronic signatures are admissible in evidence⁵, and the Law Commission concluded in 2019 that an electronic signature can be used to execute a document, provided the person signing intends to authenticate it and any other formalities are met⁶. It lists scanned handwritten signatures among the types of electronic signature.

The exceptions are the documents with extra formalities:

• Deeds: they must be signed in the physical presence of a witness, even when both use electronic signatures⁶.
• Wills: a will must be signed or acknowledged in the presence of two witnesses present at the same time⁷. A pasted image is not a safe way to sign one.
• Anyone asking for a wet signature: banks, landlords or government forms can insist on an original signed in ink.

EU eIDAS rules, kept in UK law, add that an electronic signature cannot be refused just because it is electronic, and that only a qualified electronic signature has the same effect as a handwritten one⁸. An inserted signature image is a simple electronic signature. For a PDF you send back by email, that means: for a tenancy reference, an order form or a consent form it is usually fine. For a deed or a will it is not.

Important: A digitised signature is not a qualified electronic signature. If in doubt, ask whoever receives the document whether they accept it. This article is not legal advice.

Frequently asked questions

How do I add a signature to a PDF for free?

On a PC with the free Adobe Acrobat Reader via Fill & Sign, on a Mac with Preview, on an iPhone with the Markup tools and on Android with the Acrobat app.

Can I sign a PDF without Adobe?

Yes. On a Mac with Preview, on an iPhone with Markup. On Windows, Microsoft Edge can open PDFs and lets you draw on them, but you cannot insert an image there.

How do I get my real signature into a PDF?

Sign on white paper, photograph it and turn it into a transparent PNG. Load that image as your signature in Acrobat Reader or paste it in Preview.

Can I sign a PDF on my phone?

Yes. On an iPhone via the Markup icon and Add Signature, on Android with the Adobe Acrobat Reader app.

Is a scanned signature legally binding in the UK?

For most contracts and forms, yes: English law accepts electronic signatures, including a scanned handwritten one, as long as you intend to sign. Deeds need a witness who is physically present, and wills need two witnesses, so a pasted image is not enough there.

Sources

1. 1Adobe: Sign PDF documents online (adobe.com)
2. 2Apple: Fill out and sign PDF forms in Preview on Mac (support.apple.com)
3. 3Apple: Use Markup on iPhone and iPad (support.apple.com)
4. 4Google Drive Help: Fill out PDF forms (support.google.com)
5. 5Electronic Communications Act 2000, section 7 (legislation.gov.uk)
6. 6Law Commission: Electronic execution of documents (Law Com No 386, 2019) (lawcom.gov.uk)
7. 7Wills Act 1837, section 9 (legislation.gov.uk)
8. 8Regulation (EU) No 910/2014 (eIDAS) as retained in UK law, Article 25 (legislation.gov.uk)