How to sign a PDF on your phone
To sign a PDF on your phone, open the document in an app that lets you draw a signature, draw it once with your fingertip or a stylus, place it on the signature line, resize it to fit, add the date, then export a flattened PDF and send it back.
The three things people mean by "signing" a PDF
Most everyday signing is the first kind below: an image of your handwritten signature placed on the page. The other two exist and are worth knowing about, because a form that asks for one will not accept the others.
- A drawn signature. You draw your signature and it is placed on the document as an image. This is what almost every landlord, school, clinic, and employer form means when it says "sign here".
- A typed name. Some web services render your typed name in a script typeface. It is quick, but it looks the same for everyone with your name, so many recipients prefer a drawn mark.
- A certificate-based digital signature. A cryptographic signature bound to a digital certificate, which can be verified and shows whether the file changed after signing. Government filings and some corporate processes require this specifically, and they will tell you so.
Whether a signature is legally binding depends on the document, the parties, and the laws of your jurisdiction. This guide is general information, not legal advice — consult a qualified professional about documents with legal significance.
Draw a signature that looks like yours
Sign bigger than feels natural. A fingertip is a blunt instrument compared with a pen, and a signature drawn large and then scaled down reads far cleaner than one cramped into a small box.
A few things help:
- Use a stylus if you have one; otherwise the pad of your finger, not the nail edge.
- Rest your wrist on the table and move your whole hand, rather than drawing from the fingertip alone.
- Sign in one continuous motion. Stopping mid-stroke to reposition is what produces the shaky, unconvincing version.
- Redo it until you are happy. You are drawing this once and reusing it, so a couple of extra attempts is time well spent.
In FormFill you tap Sign (or Initials), draw on the pad, and tap Use signature. With FormFill Pro your signature and initials are saved, so the next form takes one tap instead of a fresh drawing.
Put it in the right place
Sit the signature's baseline on the printed line rather than floating above it or crossing through it, and keep it clear of the printed name underneath. Signing is also the last thing you should do, after every other field is filled and proofread.
| Part of the signature block | What belongs there | Sizing habit |
|---|---|---|
| Signature line | Your drawn signature | Roughly half to two-thirds of the line's width, baseline on the line |
| Print name | Typed text, not a signature | About the size of the form's printed text |
| Date | The date you actually signed | Match the date format the form uses |
| Initials boxes | Initials, usually one set per page or clause | Noticeably smaller than the full signature |
| Title or capacity | Typed text, only if the form asks | Same size as the printed text |
Flatten before you send it back
Flatten the signed document so the signature is part of the page rather than a separate annotation layer sitting on top of it.
This matters more for signatures than for anything else you add. An unflattened annotation can be moved or deleted by whoever opens the file, and some viewers drop the layer when printing, which is how a signed contract arrives with a blank signature line. A flattened PDF shows the same thing on every device.
In FormFill, tapping Done flattens the document into a clean PDF, saves it to your library, and offers to share a copy by email, to Files, or wherever else you need to send it.
Signed documents are sensitive — keep them local
A signed form usually carries more personal information than anything else on your phone: your address, your date of birth, an account number, and your signature together in one file. That combination is worth protecting.
FormFill has no account, no login, and no cloud backend. Imported PDFs, scans, filled forms, and saved signatures stay on your device, and the finished PDF is shared only if and when you choose, through your phone's normal share sheet.
Sign once, reuse anywhere
FormFill turns any paper or PDF form into a fillable, signable document. Draw your signature and initials once, drop them onto any form in a tap, then flatten and send a clean PDF.