How to Sign a PDF on iPhone or Android in Under a Minute

How do you sign a PDF on an iPhone?

Open the PDF in Files or Mail, tap the Markup pen icon, tap + and choose Add Signature. Draw the signature with a finger, place it on the line and tap Done. Markup is part of iOS, so nothing has to be installed.

• In Mail, tap and hold the PDF attachment and choose Save to Files, then open it in Files. You can also tap the attachment and use Markup directly, which offers to reply with the signed copy.
• Tap the Markup button, a pen tip in a circle.
• Tap the + button, then Add Signature. Sign with your finger and tap Done.
• Drag the signature onto the signature line and drag the corner handles to resize it.
• Tap Done. The signature is saved into the file.

How do you sign a PDF on Android?

Android has no single built-in signing tool. The closest is the annotate pen in the Google Drive PDF viewer, which lets you draw on the page. It works, but you cannot resize or reposition the drawing precisely.

What you get depends on the phone. Recent versions of the Google Drive app show a pen button when you open a PDF. Samsung phones can annotate PDFs in Samsung Notes, with or without an S Pen. Some other manufacturers include a viewer with no drawing tools at all. In every case you draw at the scale of the page, which on a 6-inch screen means zooming far into the signature line and signing in a very small area. If the result looks shaky, or your viewer has no pen, the browser method below is the consistent route.

Any phone: sign in the browser

Sign PDF works the same on iPhone, Android and desktop. The PDF is opened and saved entirely in the browser and is not uploaded, which matters for employment contracts and tenancy agreements. Files up to 100 MB are accepted.

• Open Sign PDF and choose the document from Files, Downloads or Google Drive.
• Tap Signature and create it: draw with your finger, type your name, or upload a photo of your signature on white paper.
• Drag the signature into place and resize it with the corner handles.
• Use the Initials, Date and check mark buttons for the other boxes the form asks for.
• Download the signed PDF and attach it to your reply.

Which signing method fits your situation?

Use iPhone Markup for a quick one-off, the browser tool when you need initials, dates and precise placement on any device, and a dedicated e-signature platform only when the other party requires an audit trail.

Tips for a signature that looks right

• Turn the phone sideways when drawing. The wider canvas gives a more natural stroke.
• Sign slowly and larger than you think, then shrink it on the page. Small, fast finger signatures look jagged.
• For an uploaded photo, sign with a thick black pen on plain white paper in good light, so the background can be removed cleanly.
• Match the line. Most signature boxes are about 5 to 7 cm wide, so keep the signature from spilling over nearby text.
• Zoom in on the page before placing the signature. Positioning is much easier at 200% than at full-page view.
• Use blue or black ink. Blue makes it obvious which marks were added to a black-and-white form, and some offices prefer it for that reason. Avoid light colours, which vanish when the page is photocopied or faxed.

Signing with several signers, or for someone else

When two people have to sign, the simplest route is a relay. The first person signs and sends the file on, and the second adds their signature to that copy. Do not flatten the PDF until the last person has signed if it contains form fields that still need filling in. Only place another person's signature with their clear permission, and say so in the covering email. For company documents that need signatures from several directors, an e-signature platform with a signing order is worth the setup.

Is a signature added this way legally valid?

Usually yes. In the US, UK and EU, a simple electronic signature, including an image of your handwriting placed on a PDF, is accepted for most everyday agreements, provided it is clear that you intended to sign.

In the United States the ESIGN Act of 2000 says a signature cannot be denied legal effect only because it is electronic. In the EU, the eIDAS regulation defines three levels: simple, advanced and qualified. A drawn, typed or image signature is the simple level. It is valid, but if it is ever disputed you may need other evidence, such as the email thread, to show that you were the one who signed.

Some documents need more. Certain property deeds, wills, notarised papers and court or government filings may require wet ink, a witness, or a qualified digital signature. If the sender specifies a method, follow it. For a high-value contract, ask before signing.

Before you send it back

Scroll through the whole document. Forms often hide a second signature line or an initials box on a later page, and a missed box means the whole thing comes back. If the PDF has fillable fields, complete them with Fill PDF Form first, then sign.

Consider running the finished file through Flatten PDF. Flattening turns field entries and annotations into ordinary page content, so they display the same in every viewer and cannot be dragged around by accident. Keep a copy of the signed version for yourself, named with the date, so you are not relying on the other side's records. If the file is going by email and contains personal details, Protect PDF adds a password with AES-256 encryption. Send the password by a different channel.

Troubleshooting

• The PDF asks for a password: enter it when prompted. A file that restricts editing must be unlocked with its password in Unlock PDF first.
• The signature has a white box around it: use the Remove white background option when uploading, or draw it instead.
• The signature looks blurry when printed: it was drawn small and enlarged. Draw it large and shrink it on the page.
• The recipient cannot see the signature: some mail previews hide annotations. Flatten the PDF and send it again.