How to sign a PDF attachment in the Gmail app on iPhone

A contract lands in Gmail on your phone. You tap the attachment, it opens in a viewer, and you go looking for the pencil icon every article on the internet told you to tap.

It isn’t there.

That’s not you missing it. The Gmail app on iOS renders PDFs in its own viewer, not Apple’s — and Apple’s Markup tools only exist inside Apple’s preview. So the standard “tap the attachment, tap Markup, add your signature” instructions are written for the Mail app and quietly fall apart in Gmail. Same phone, same PDF, different viewer.

The fix is one extra step, and after that everything works normally.

The free route: get the PDF out of Gmail first

Markup can absolutely sign this document. It just can’t reach it while the file lives inside Gmail’s viewer. So move it:

Open the email in Gmail and tap the PDF attachment to open the preview.
Tap the share icon (the box with the upward arrow) in the top corner. If you don’t see it, tap the download arrow first — the file lands in Gmail’s own storage and the share icon appears.
Choose Save to Files and pick a folder you’ll remember. On iCloud Drive or On My iPhone → Downloads are both fine.
Open the Files app and tap the PDF.
Tap the Markup icon (the pen tip, top right).
Tap + → Signature. Draw one with your finger, or pick a signature you’ve saved before.
Drag it onto the signature line, resize with the corner handles, and add the date as a Text box if the form asks for one.
Tap Done, then the share icon → Save (it writes back to the same file).

That’s the whole free answer. No app, no account, no upload — Markup is on every iPhone and it does the job properly once the file is somewhere it can see.

Shortcut worth knowing: from step 2 you can skip Files entirely and send the PDF straight into a signing app from the same share sheet. Saving to Files is the reliable route to describe; the share sheet is the fast one once you know which app you want.

Sending it back — the bit that also trips people up

The signed copy is now sitting in Files, not in Gmail. To reply with it:

Open the original email in Gmail and tap Reply.
Tap the paperclip in the compose bar.
Choose Attach file → browse to the signed PDF in Files (not Insert from Drive, unless you deliberately saved it to Drive).
Check the attachment name and size look right before you send. A common mistake is re-attaching the unsigned original, which is sitting in the same folder under a nearly identical name — rename the signed copy contract-signed.pdf while you’re in Files and you’ll never make that mistake.

Open the attachment one more time from the sent mail and scroll every page. It costs ten seconds and it’s the only way to know the signature actually saved rather than living in an unsaved annotation layer — the same failure mode behind flattening a signed PDF before you send it.

Outlook, Yahoo Mail and the rest

The situation is identical in every third-party mail app on iOS, for the same reason — each ships its own attachment viewer:

Outlook — tap the attachment, then the ⋯ or share icon → Save to Files (Outlook also offers Open In, which is the fast route into a signing app). No Markup pencil in the viewer.
Yahoo Mail — tap the attachment → share icon → Save to Files. Same detour.
Spark, Proton Mail, Edison and friends — same pattern. If you can reach an iOS share sheet, you can reach Markup.

The one exception is Apple’s own Mail app, where Markup is built right into the attachment preview and there’s no detour at all. If some of your paperwork arrives there, that flow is a genuinely faster one — and it’s why the advice you found didn’t match your screen.

Where the free route starts costing you time

Markup is fine for a signature or two a year. Honestly, that’s most people, and if it’s you, stop reading.

It gets tiring when signing becomes routine, and always in the same three places. The signature is a raw finger-drawing, so a version you’re happy with takes a few attempts on glass every time. Dates, initials and your printed name are individual text boxes you create, size and nudge by hand. And a ten-page agreement wanting initials in the corner of every page is ten separate placements, each one drawn slightly differently from the last.

Doing it in Signed

Signed picks the file up at the same share sheet, so the Gmail detour collapses into a single tap:

In Gmail, tap the attachment → share icon → Signed.
Tap your saved signature and drop it on the line. You create it once — drawn properly, typed in a real handwriting style, or generated from your name — and it’s identical on every document afterwards.
Add the date, initials, printed name or a checkmark from the same tray. They’re one tap each, not new text boxes.
Tap Finish for a clean, flattened PDF, then share it back into a Gmail reply.

There’s no Gmail integration or account connection involved, and there shouldn’t be — the file arrives through the standard iOS share sheet like any other document, and the PDF never leaves your iPhone. Contracts and offer letters go through email precisely because nobody wants a third copy on somebody’s server.

Can I sign it without saving it anywhere? No. Something has to hold the file while you annotate it — either Files or a signing app. Gmail’s viewer is read-only by design.

Will the recipient see my edits as comments? Not if you export properly. Markup’s Save writes a normal annotated PDF that opens the same everywhere; Signed exports a flattened copy where the signature is part of the page.

The PDF won’t open at all in Gmail. It’s probably password-protected — that’s a different job, and you’ll need the password before any of this works.

Do I need to print and rescan it? No, and please don’t — a rescan makes the document blurrier and no more official.

One honest note

Signed is a signing tool, not legal advice. For everyday paperwork — leases, NDAs, school forms, freelance contracts — a signed PDF returned by email is how most of the world does business. For documents with real legal weight, like a will, a power of attorney or a property deed, a notary or witnesses may be required depending on where you are, and a signature added on a phone doesn’t change that. Check what your document actually needs before you send it back.