How to sign a PDF that has no signature field on iPhone

You’ve been sent a PDF to sign. You open it, scroll to the bottom, and there’s the line — Signature: ________ — but tapping it does absolutely nothing. No box, no prompt, no “sign here” arrow. The last document you signed had one of those. This one doesn’t.

Here’s the thing nobody tells you upfront: a PDF doesn’t need a signature field to be signed. The field isn’t what makes a signature work. You can put your signature anywhere on any page of any PDF, on the iPhone you’re holding, in about a minute, and the finished file is a perfectly normal PDF that anyone can open.

The rest of this page is how, plus the one genuine exception where the missing field really does matter.

Why you expected a field in the first place

If you’ve signed something through DocuSign, Dropbox Sign or a similar service, you’ll have seen a yellow “Start” tag pointing at a box, with a Sign button that fills it in. That experience trains you to look for a target. When you get a plain PDF by email instead, the absence of that target reads as this document isn’t ready yet.

iOS reinforces it. When a PDF genuinely does contain interactive form fields, opening it in Files gives you a bar across the top offering to fill the form in, and tapping a field pops the keyboard. When the PDF has no fields, that bar simply never appears — and there’s no message explaining why. You’re left with a document that looks fillable and behaves like a photograph.

Both cases come from the same underlying fact: those tagged boxes are something the sender’s software adds. A plain PDF exported from Word, Pages, or a scanner has none of them, and never will. So the sender hasn’t forgotten anything. There is nothing missing from your copy. The document is just a document.

And a signature, on a document, is ink on top of the page. That’s all it has ever been on paper, and it’s all it needs to be here.

The free way: iOS Markup

Your iPhone can do this with nothing installed and no account:

Open the PDF in Files, or tap the attachment directly in Mail.
Tap the Markup icon — the pen tip inside a circle, top right.
Tap + (bottom right) → Signature.
If you’ve never done this before, you’ll get a blank card to sign on. Turn the phone sideways, sign with your finger, tap Done. It’s saved for next time.
Your signature drops onto the page. Drag it to the line and use the blue corner handles to size it.
Need the date too? + → Text, tap the box, Edit, type it, drag it into place.
Tap Done, then Share to send it back.

That’s the complete answer for a one-off document, and if that’s what you came here for you can genuinely stop reading. It costs nothing, it works offline, and the recipient gets an ordinary signed PDF.

Where Markup gets tiring, honestly. The saved signature is a single image at a single quality — whatever your finger managed on the day — and re-signing to improve it means deleting the old one. Sizing is by hand every time, so a document that needs your signature and initials and a date on four pages becomes a lot of pinching. Initials aren’t a concept Markup has at all; you either draw them into the signature card as a second entry or type them as text. And Markup annotations aren’t always flattened into the page, which is its own occasional problem — what to do when a signature moves or disappears covers that.

The app way, when this keeps happening

Signed is built for the repeat case, and it treats the missing field as a non-event, because in Signed there are no fields to begin with — you tap where you want something and it goes there.

Import the PDF (Files, Photos, Mail, or scan a paper copy with the camera), then place what the document asks for: your signature, your initials, today’s date, your printed name, a checkmark, or free text. Each of those is saved once and reused on every document afterwards, so the tenth form is as fast as the second. Export produces a flattened PDF — the signature is baked into the page, not a draggable sticker.

Your signature can be one you draw with your finger, one you type and style in real handwriting fonts, or one the AI generates from your name — there’s a free web version of the generator if you want to see the styles before installing anything. And the documents never leave your iPhone: no upload, no account, no copy of your paperwork on somebody’s server.

If the document also has a stack of blanks to complete before the signature, filling out and signing a form on iPhone is the fuller walkthrough — and if tapping the blanks does nothing either, that’s the same root cause as this page and why you can’t type in a PDF on your iPhone sorts out which of four problems you actually have.

The one exception: a certificate signature field

There is a case where the missing field is real, and it’s worth knowing so you don’t waste an afternoon.

Some documents — often from banks, law firms, or government processes — carry a digital signature field: a box that, on a desktop, says something like “Click to sign” and expects a cryptographic certificate rather than a picture of your handwriting. That’s a fundamentally different mechanism. It verifies who signed using a certificate you’d have to be issued, and it can detect whether the file changed afterwards.

You can tell them apart quickly: if the sender’s instructions mention a certificate, a digital ID, a smart card, or a specific piece of software, it’s this kind. If the PDF opens read-only and refuses your annotations, that’s another tell — see signing a password-protected or restricted PDF.

An iPhone can’t fill that kind of field, and neither Markup nor Signed pretends to. Drawing a signature on top of such a document doesn’t complete it — and if the file already carries somebody’s certificate signature, adding marks can invalidate it. The honest move is to reply to the sender and ask what they need, rather than sending back a file they’ll have to reject.

This is rare. The overwhelming majority of “please sign and return” PDFs are ordinary documents and the Markup or Signed route above is exactly right for them.

Which one you’ve got, in ten seconds

What happens when you open it	What it is	What to do
Tapping the signature line does nothing	A plain PDF — no fields at all	Markup or Signed; place a signature on top
A bar offers to fill the form, and taps open a keyboard	An interactive form, just with no signature widget	Fill the fields, then place the signature on top the same way
It opens read-only, or Markup is greyed out	Restricted or certificate-signed	Check here first
The sender mentions a digital ID or certificate	A certificate signature field	Ask the sender — an iPhone can’t do this one

The short version

A missing signature field is not a problem to solve. Plain PDFs never had one.
Free: Files or Mail → Markup → + → Signature → drag it onto the line → Share.
Repeat use: an app that saves your signature, initials and date and flattens the export saves the fiddling — that’s what Signed does.
The exception: certificate-based signature fields are a different mechanism and need the sender’s software, not your phone.

One honest closing note, since the question sits behind this one: putting your signature on a document doesn’t by itself make it official, and having a tidy field to sign in wouldn’t have either. What any specific document actually requires — a witness, a notary, a particular service — depends on the document and where you are. Here’s how we think about that. Signed is a signing tool, not legal advice.