A lease, a school permission slip, a consent form from the dentist: the email says "please sign and return," and the printer at home has been out of ink since spring. You don't need it. Your iPhone can fill in a PDF form and sign it with your finger, and the result is an ordinary PDF anyone can open.
How do I sign a PDF on iPhone?
Open the PDF, tap Add Signature in the Markup tools, sign with your finger, and drag the signature onto the line. The full steps:
- Open the PDF. On iOS 26 and later, it opens in the Preview app; on older versions, in Files. If it's an email attachment, just tap it.
- Tap the Markup button (the pen tip), then the Add button (+). In Preview, the Add button sits in the toolbar along the bottom.
- Tap Add Signature. Pick a signature you've saved, or sign a new one with your finger and tap Done. Turn the phone sideways for more room.
- Drag the signature onto the signature line. Drag the blue dots on its corners to make it the right size.
- Tap Done, then save it, or tap Share to send it straight back.
That's it. The signature becomes part of the PDF, so it shows up for whoever opens it, on any device. Not on your iPhone? The free sign PDF tool does the same in any browser, without uploading the file.
Fill out the form fields first
Most forms want more than a signature: your name, the date, an address. Fill those in before you sign.
In Preview (iOS 26 and later):
- Open the PDF form in Preview.
- Tap the Form Filling button.
- Tap a field and type. If an AutoFill suggestion with your details appears above the keyboard, tap it.
- In a signature field, you can sign right in the field with your finger.
In Files (any recent iOS): open the form, tap the AutoFill button, tap a blank field and type. Keep going field by field. If a prompt offers to fill several related fields at once, review what it suggests, fix anything wrong, and tap Fill.
AutoFill pulls from your My Card in Contacts, so it's worth making sure that card has your current address. You can also tap Choose other to fill in someone else's details from your contacts, such as a child or a parent you're filling the form out for.
When the form has no fields
Plenty of PDFs aren't real forms: they're scans of paper, with blank lines that don't react when you tap them. You can still fill them in.
- Tap the Add button (+).
- Tap Add Text Form Box.
- Drag the box onto the blank line and type.
- Use the formatting tools to change the size or font so it fits.
Add one box per line, then sign as above. If the document arrived as a photo rather than a PDF, convert it first with the photo-to-PDF steps, then sign the PDF.
Save more than one signature
iPhone keeps the signature you draw and offers it again next time. You can keep a few: your full signature, your initials for every page of a lease, and a different style if you sign in two scripts.
- Add another: in Add Signature, tap Add or Remove Signature, then the Add button, and sign again.
- Label it: tap the menu next to New Signature and choose a label such as initials or nickname.
- Delete one: tap Add or Remove Signature, then the Delete button next to it.
A saved signature is a picture of your signature on your phone. Anyone who unlocks your iPhone can place it, which is one more reason to keep a passcode on it.
Send it back
When the form is filled and signed, tap the menu in the document and choose Export or Share, or reply to the email with the PDF attached. Before you press Send, open the attachment once and check that the signature and every field are actually there; some forms built for desktop software show filled fields on your phone and blanks everywhere else.
If what you're sending includes your ID number, bank details or health information, think about the channel as well as the file. There's a short guide to that: sharing documents securely from your iPhone.
Common problems
I don't see Add Signature. Tap the Markup button first; the Add button lives in the Markup toolbar. In some apps the toolbar starts minimized. Tap it to expand.
The fields won't take text. The PDF has no real form fields, or it's locked for editing. Use Add Text Form Box instead. If the PDF asks for a password, you'll need it from the sender.
The signature is huge or in the wrong place. Tap it to select it, drag it, and pull the blue dots in to shrink it. To start over, tap the More button and choose Undo.
I need to change something after signing. Undo while the document is still open, or keep an unsigned copy. In Preview you can make one first: tap the menu next to the filename and choose Duplicate. For other changes, such as removing a page or adding a missing one, see how to edit a PDF on iPhone.
They need it on paper after all. Sign on the phone anyway, then print the signed PDF when you're near a printer. It's the same file.
Keep the signed copy where you'll find it
The signed version is the one that matters, and it's usually the one that disappears: it went out as an email attachment and now lives in your Sent folder, three months deep. When the landlord asks about the deposit clause or the school wants the form again, you're searching email for "signed."
Paperlock is a private place for exactly those copies. Save the signed PDF to it and it reads what the document is, who it's from and any dates that matter, files it under a clear title, and keeps it behind Face ID. It won't sign or fill forms for you (your iPhone already does that well); it makes sure the signed result is findable later, by asking for it in plain English.