How to sign a PDF on any device

Before you sign

• Read the whole document. Signing electronically is as binding as signing on paper in most situations.
• Check what’s being asked. Some documents need a signature, a printed name, a date and initials on each page. Others ask for a specific signing service, or for a witness.
• Keep the original. Sign a copy, so you can start again if something goes wrong.
• Unlock it if needed. If the PDF is password-protected, you’ll need the password to edit it. Some PDFs allow viewing but block changes.

Sign a PDF online on any device

A browser-based editor works the same way on Windows, Mac, Chromebook, Linux, iPhone and Android. With ToolsMotive Edit PDF, the file is opened and saved by your browser, so it doesn’t need to be uploaded to a server.

1. Open Edit PDF and drop your PDF into the box, or tap Select a PDF.
2. Go to the page with the signature line.
3. Add your signature in one of two ways:
   • Draw it: choose Draw, pick a colour (blue or black looks most natural), and sign with your mouse, trackpad or finger.
   • Use an image: add a PNG or JPG of your handwritten signature (see the next section for making one).
4. Position it. Choose Select, drag the signature onto the line and use the corner handle to resize it. Undo or delete if you need another try.
5. Add the date and your name with the Text tool if the form asks for them.
6. Save and download. The editor writes a new PDF and checks it opens with the right number of pages.

The signature is added to the page as part of the PDF content, so it shows in every PDF reader. It’s a visible signature mark; it isn’t a certificate-based digital signature (explained below).

Making a clean signature image

A signature image you can reuse looks more natural than a mouse drawing and saves time.

1. Sign on plain white paper with a dark pen. A fine felt-tip or gel pen gives a clean line.
2. Photograph it in good, even light, holding the phone directly above to avoid a slanted result.
3. Crop tightly around the signature in your phone’s photo editor.
4. Keep it small. A width of 600–1,000 pixels is plenty; use Resize image if the photo is huge.
5. Remove the background if you want it to sit cleanly on coloured or lined forms. A PNG with a transparent background looks best.

Store the image somewhere private. Anyone who has it can paste it onto a document, which is one reason why higher-value agreements use signing services that record who signed and when.

Sign a PDF on a Mac with Preview

Preview, the app that comes with macOS, has a built-in signature feature. Apple’s guide, Fill out and sign PDF forms in Preview on Mac, describes the current steps; in short:

1. Open the PDF in Preview.
2. Show the Markup toolbar and click the Sign button.
3. Create a signature with the trackpad, by holding a signature up to the camera, or (on recent versions) with an iPhone or iPad nearby.
4. Click the signature to add it, then drag and resize it.
5. Save, or use File → Export as PDF to keep the original unchanged.

Preview stores your signatures for next time. For a Mac without Preview’s newer features, or to sign on a work computer where you can’t install apps, the browser method above works too.

Sign a PDF on iPhone, iPad or Android

• iPhone and iPad: open the PDF in the Files app or from Mail, tap the markup (pen) icon, then the plus button and Add Signature. Sign with your finger, then place it.
• Android: the tools depend on your phone and apps. Many PDF viewers have a signature or draw feature; otherwise use a browser-based editor.
• Any phone: open Edit PDF in your browser, choose Draw and sign with your finger. Turning the phone sideways gives you more room.

Signing with a finger on a large screen usually looks better than with a mouse. A cheap stylus helps even more.

Filling in the rest of the form

Most documents that need a signature also need a few details:

• Text fields: some PDFs have fillable fields; click and type. If not, use a Text tool to place text on the lines.
• Ticks and crosses: type an “X” or “✓” with the Text tool, or draw one.
• Mistakes on the form: the White-out tool covers something with a white box. Note that it covers rather than deletes: the original content can still exist underneath in the file. To truly remove sensitive content, a proper redaction tool is needed.
• Extra pages: if the form has pages you don’t need to send, remove them with Delete PDF pages; if you need to attach documents, combine them with Merge PDF.

Is an electronic signature legally valid?

In many countries, yes, for most everyday documents. Two major examples:

• United States: the Electronic Signatures in Global and National Commerce Act of 2000 (ESIGN) says a signature or contract can’t be denied legal effect solely because it’s in electronic form (Public Law 106-229, govinfo.gov). It lists exceptions, such as wills and certain court and family-law documents, and most states have similar laws.
• European Union: the eIDAS Regulation sets out three levels: simple electronic signatures, advanced electronic signatures and qualified electronic signatures. A qualified signature has the same legal effect as a handwritten one across the EU (European Commission, eIDAS Regulation).

What matters in a dispute is usually evidence: that you intended to sign and that the document wasn’t changed afterwards. A drawn signature on a PDF sent by email is often enough for everyday agreements, forms and letters. For property, large financial commitments, regulated industries or anything with formal requirements, follow the method the other party or the law requires. This is general information, not legal advice.

Electronic signature vs digital signature

The terms are often used loosely, so if someone asks for a “digital signature”, check which they mean. Wikipedia’s article on electronic signatures explains the categories in more depth.

Sending the signed PDF

• Check it. Open the signed file on another device or app to make sure the signature appears in the right place.
• Name it clearly, for example lease-agreement-signed-2026-11-07.pdf.
• Keep it small. A signature image can make a file bigger; if it’s over an email or upload limit, use Compress PDF.
• Keep a copy of exactly what you sent, together with the email or message you sent it with. If there’s ever a question about what was agreed, the signed file and the record of sending it are your evidence.
• Send it the way it was requested. Some organisations want signed forms uploaded to a portal rather than emailed; using their channel avoids delays.

Common mistakes

• Signing the only copy and then needing to redo it.
• A huge signature image that bloats the file.
• Covering text with the signature or a white box.
• Assuming white-out deletes content. It hides it visually.
• Using a simple signature where a qualified or witnessed one is required.