How to Fill and Sign a PDF Form on Your Phone (Android and iPhone)

The email says “please fill in the attached form, sign it and send it back by Friday.” A few years ago that meant a printer, a pen and a scanner. Today the whole thing can be done on the phone in your hand, often in less time than it takes to find a working printer.

There are a couple of traps, though. Some forms have proper fill-in boxes and some are just pictures of paper. Some answers vanish when the other person opens the file. And a signature added the wrong way can look like a blurry sticker. This guide covers all of it.

First, find out what kind of form you have

Everything else depends on this. PDF forms come in three types, and you can usually tell which one you have within a few seconds of opening it.

Most bank, school, visa and HR forms are the first type. Forms people make by scanning a paper original are the second. XFA forms are rarer now but still turn up on some older government sites.

Filling a fillable form

Open the form in Fill PDF Form. The fields are highlighted, so you can see at a glance what needs an answer.

1. Work through the fields.

   Tap a box and type. Tick boxes and radio buttons respond to a tap, and drop-down lists open a picker. Fields that share a name, such as your name on every page, fill together.

2. Use “Next empty field”.

   On a phone screen it is easy to miss a box on page 3. The progress counter and the jump button take you to whatever is still blank.

3. Decide about flattening.

   Leave Flatten the form unticked if you or someone else will change the answers later. Tick it for the final copy you send, so nobody can edit your answers afterwards.

4. Save the filled PDF.

   The answers are written into the form’s own fields, so the file opens filled in Adobe Reader, Chrome, Edge, Preview and phone apps.

Filling a scanned or flat form

Here there are no boxes to tap, so you place the answers yourself. In the same tool:

• Choose Type text and tap on the first line to type an answer. Then double-tap each empty spot for the next one, so you don’t have to keep switching modes.
• Use Tick, Cross or Dot for check boxes, and Date for today’s date.
• Use Image for a passport photo or a picture of a stamp.
• Tap an answer to move it, resize it or change the font. Handwriting fonts are available if a typed answer looks out of place on a handwritten form.

Adding your signature

Once the answers are in, open the saved form in Sign PDF. You have three ways to create a signature:

• Draw it with your finger or a stylus. It is saved as a smooth vector shape, so it stays sharp when printed or zoomed.
• Type it and pick a handwriting-style font. Fine for internal forms; some organisations prefer a drawn signature.
• Upload a photo of your signature on white paper. The paper, shadows and lines are removed so only the ink remains, with no white box around it.

Drag the signature onto the line and resize it to fit. Add your initials, the date or your printed name the same way. If every page needs initials, the sign every page option does it in one tap.

You can also add a signature image directly inside Fill PDF Form with the Image option, which is handy for a quick one-page form.

Before you send it

1. Open the final file in a different app. Your phone’s default PDF viewer is fine. If an answer is missing there, it will be missing for the recipient too.
2. Check the size. Many portals and some email systems choke on large attachments. Compress PDF for Email or Compress PDF to 1 MB usually solves it without visible quality loss.
3. Name the file sensibly. “Ali-Raza-Admission-Form-signed.pdf” beats “document(3).pdf”, and the person processing it will thank you.

Using your phone’s own apps

You may already have something installed that can do part of the job:

• Android: the Google Drive app has been able to fill basic fillable PDF forms since 2019. It works for simple forms but not for scanned ones, and the file lives in your Drive.
• iPhone and iPad: open the PDF in the Files app and use Markup to add text and a signature. Recent versions of iOS can also detect form fields and suggest your details automatically.

These are fine for straightforward forms. A dedicated form filler earns its place with scanned forms, forms that must open filled in every viewer, flattening, and keeping everything on the device instead of in an account.

Is a signature drawn on a phone legally valid?

For most everyday paperwork, yes. Electronic signatures are recognised in many countries, for example under the ESIGN Act in the United States and the eIDAS regulation in the European Union. Courts generally care that you intended to sign and that the document wasn’t changed afterwards.

There are exceptions. Some documents, such as wills, certain property deeds and some court or government filings, may require a handwritten signature, a witness or a certificate-based digital signature. A drawn signature is an electronic signature, not a certified digital signature. If the stakes are high, check what the receiving organisation accepts. This is general information, not legal advice.

Forms with a photo box

Admission, visa and job forms often have a box for a passport-size photo. Crop your photo to the right shape first with Crop Image, so a face isn’t squeezed into a rectangle. Then use the Image option in Fill PDF Form, tap the box and resize the photo to fit inside its border. Check the requirements printed on the form: some ask for a plain white background or a recent photo, and no tool can fix that afterwards.

Common mistakes

• Typing on top of a fillable field. If the form has real fields, use them. Text placed over a field can end up hidden behind it in other viewers.
• Flattening too early. Once flattened, answers can’t be edited as fields. Keep an unflattened copy until you are sure.
• Letting autocorrect “fix” your name. Check names, email addresses and ID numbers character by character.
• Getting the date format wrong. Forms from different countries expect DD/MM/YYYY or MM/DD/YYYY. Copy the format shown on the form.
• Sending the unsigned version. Phones save files with similar names. Open the attachment before you hit send.

Frequently asked questions