To sign a document someone sent you by email, first check how it arrived. If it’s a PDF attachment, open it in a tool that adds signatures (Markup on an iPhone or Mac, or the free Acrobat Reader anywhere), sign it, and reply with the signed copy attached. If it’s an e-signature request with a “Review” or “Sign” link, click the link and follow the steps on the page. Either way, there’s no printer or scanner involved.

The two cases feel similar from your inbox, but they work differently, and mixing them up is how people end up printing things they didn’t need to.

Is it an attachment or a signing request?

An attachment is a file sitting in the email, usually a PDF or Word document, that you have to open, sign and send back yourself. A signing request is an email from an e-signature service with a button or link and no file to download. The signing happens on the service’s web page, and the service sends the finished copy to everyone.

If you see a paperclip and a file name, it’s an attachment. If the email comes from a signing service and the main thing in it is a button, it’s a request. Requests are easier on you as the signer, because the sender has already marked where to sign.

How do I sign an email attachment on an iPhone?

Tap the attachment in the Mail app, tap the Markup button, add your signature, then tap Done and choose to reply to the sender. Apple’s guide says you can “draw and write on a photo, video, or PDF attachment, then save it or send it back.” When you’re finished, Mail offers four choices: reply to the attachment sender, start a new message, save the annotated attachment to your files, or discard it.

To use a saved signature rather than drawing freehand, tap the Add button in the Markup toolbar and choose Add Signature. For forms with fields to type into, Apple describes a shortcut: tap the attachment, tap the AutoFill button, tap Form Filling, fill in the fields, then tap the Done button and Reply to [name].

Before you start, it’s worth saving a copy of the original. Touch and hold the attachment and choose Save to Files. The full walkthrough, including signing in the Files app, is in how to sign a document on iPhone.

How do I sign an email attachment on a Mac?

Start a reply, attach the PDF to it, hover over the attachment, and choose Markup from the button that appears in its upper-right corner, then use the Sign tool. Apple’s Mail guide says that “when you’re writing a message and add an image or PDF document, you can use Markup to write or draw on the attachment” and add a signature.

A few details from Apple’s page:

  • If the Markup option doesn’t appear, you may need to turn it on in System Settings > General > Login Items & Extensions, under Extensions.
  • The Sign tool lists signatures you’ve already created. To make a new one, Apple points you to Preview’s instructions for filling out and signing PDF forms.
  • You can change your annotations until you send. After that, Apple says, “your annotations become part of the image or PDF, and you and your recipients can’t modify them.”

If you prefer, save the attachment, open it in Preview, sign there, and attach the signed file to your reply. Same result.

How do I sign an email attachment on Windows or another computer?

Download the attachment, open it in Adobe Acrobat Reader (free), use Fill & Sign to add your signature, save, and attach the saved file to your reply. Adobe’s steps: select Add signature, “type or draw your signature,” select Save, then click where it should go.

One warning from Adobe that catches people: “Once you add a signature or an initial to a form and save it, you cannot edit it again.” Keep the unsigned original from the email in case you need to redo it.

If you don’t want to install anything, our free Sign a PDF tool does the same job in your browser without uploading the file. Download the signed copy and attach it to your reply. Our guide on how to sign a PDF online compares these options in more detail.

What if the attachment is a Word document?

Ask the sender for a PDF if you can. A PDF looks the same on every device, so what you sign is what they’ll see. If you’re working in Word yourself, how to insert a signature in Word covers the options, and if someone shared a Google Doc rather than attaching a file, see how to add a signature in Google Docs.

How do I sign a document from an e-signature request email?

Open the email, click the link, fill in the highlighted fields, adopt a signature, and confirm. The labels vary by service, but the pattern is the same. Google’s eSignature help describes its signer steps like this:

  1. Open the email notification and click the embedded link.
  2. Fill in any text fields you’ve been asked for, such as a job title.
  3. Click the colored fields, which are the ones assigned to you.
  4. Create your signature by typing your name or drawing it with your “mouse, trackpad, or touchscreen,” then click Adopt and sign.
  5. Click Mark Complete, review and accept the terms, and click Agree & Continue.

When everyone has signed, Google says all signers and the requester get an email that the request is complete, and the final PDF ends with an audit trail page. That’s the main advantage of a request over an attachment: you don’t have to keep track of which version you signed, because the service keeps the signed copy and the record of when it happened.

One habit worth building: check that the request came from someone you expected. If an email asks you to “sign” something you never discussed, contact the sender another way before clicking.

Is my email signature the same as signing a document?

No. Your email signature is the block at the bottom of your messages. Microsoft’s Outlook help describes it as something that can include “text, links, pictures, and images (such as your handwritten signature or a logo),” which you can choose to add automatically to new messages, replies and forwards. Even with an image of your handwriting in it, it isn’t signing anything, because it goes on every email it’s set up for.

What makes something a legal signature in the US is intent. Federal law defines an electronic signature as a sound, symbol or process “executed or adopted by a person with the intent to sign the record” (15 U.S.C. § 7006). An automatic footer shows no particular intent.

Can I reply “I agree” instead of signing the document?

Sometimes, but it’s the weaker option. A reply like “I accept the attached quote, Sam Rivera” can work as an electronic signature for an everyday agreement, because it shows you meant to agree to something specific. We go through when that holds up in is a typed name a legal signature.

Here’s a hypothetical. Sam’s landlord emails a one-page lease renewal with a signature line and asks for it back by Friday. Sam could reply “Looks good, I agree,” but the landlord asked for a signed document, and if there’s ever a question about the rent figure, a signed PDF of the exact page is much easier to point to than an email that says “looks good.” Sam opens it on his phone, adds his signature with Markup, and replies with the signed file. That takes two minutes and leaves no room for argument.

If you’re on the other side, sending documents out by email and chasing signed copies back, that’s the problem SignWren solves: one link per signer, one sealed copy for everyone. You can start free.