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How to fill in a PDF form

Application forms, registration forms and declarations often arrive as PDFs. You can fill them in without printing them, on a phone or a computer, and keep your answers neat and readable. This guide covers forms with fields you can type into, and PDFs that are just flat pages.

Updated October 23, 2026 · 3 min read

Fillable form or flat page?

Some PDFs are fillable forms: they contain boxes made to be typed into, ticked or chosen from a list. When you open one in PDF Tools, a line at the top tells you how many there are, for example 6 fields to fill.

Other PDFs are flat pages, such as a scanned form or a document that was simply printed to PDF. PDF Tools tells you when a PDF has no fillable fields. You can still write on it: use Text, Date and Tick to add your answers exactly where they belong.

Fill in a form

  1. 1Open Fill PDF and choose your form. It opens in the studio in Fill mode.
  2. 2Tap or click a field and type. Checkboxes, round option buttons, drop-down lists and larger boxes for longer answers all work as you’d expect.
  3. 3When you are done, tap Apply. A short window called Apply your answers appears.
  4. 4Choose whether to tick Lock the answers (see below), then tap Apply again.
  5. 5Tap Download. The file is saved with “filled” added to its name, for example application-filled.pdf.

Fill in seconds with My details

Most forms ask for the same things again and again: your name, phone number, email, address. Tap My details and enter them once. You can keep your full name, first and last name, email, phone, address, city, country, ID or passport number, date of birth, company and job title.

Tap Save and fill the form, and PDF Tools fills the empty fields that match what you saved, then tells you how many it filled. Fields that ask for a date can be filled with today’s date. Anything you already typed is left alone.

When you type something new into a field that looks like one of your details, PDF Tools offers to remember it. Your details are kept on this device only, and you can change or clear them in My details at any time.

Lock the answers, or keep them editable?

Lock the answers turns the fields into plain text on the page. Nobody can change your answers afterwards, which is useful when you send a form to an office or a bank. The catch is that you can’t change them either.

Sign it and add attachments

After you apply your answers, the form stays open. Switch to Sign at the top to add your signature, or go back to Pages and use Add files to attach a copy of your ID or a supporting document. You can reorder or delete pages and the form stays fillable, even when it is merged with photos or other PDFs. If you merge two copies of the same form, each keeps its own answers.

Forms a browser can’t fill

A few official forms use an older format called XFA, which browsers can’t fill. PDF Tools recognises these and says so. Open them in Adobe Acrobat Reader instead, or use Text to write your answers on top of the page.

Questions

Are my details sent anywhere?

No. The form is filled on your device, and the details you save in My details stay on this device.

Why does it say my PDF has no fillable fields?

The PDF is a flat page, often a scan. Use Text, Date and Tick to write on it wherever you need to.

What does Lock the answers do?

It turns each field into ordinary text on the page, so the answers can no longer be edited by anyone, including you.

Can I fill a form on my phone?

Yes. Tap a field to type with your phone’s keyboard. My details is especially handy on a phone, where typing the same address again is slow.

Try it now

Free, in your browser, and your files stay on your device.

Open Fill PDF