All guides

How to fill out a PDF form online (fillable or not)

Published October 28, 2026 by Jason Nel

Application forms, school forms, tax forms and contracts often arrive as PDFs. You don’t need to print them, fill them in by hand and scan them back. This guide covers both kinds of PDF form, signing, and what to do before you send it.

Fillable or flat? Find out first

  • A fillable form has form fields built in. When you open it, boxes are often highlighted, and clicking one gives you a typing cursor.
  • A flat form is a picture of a form: a scan, or a PDF exported without fields. Clicking does nothing, and the boxes are just lines on the page.

Open the form in Fill PDF form. If it has fields you can type straight into them; if it doesn’t, use Edit PDF as described below.

Filling in a fillable PDF form

  1. Open Fill PDF form and choose the form. It stays in your browser, so your personal details aren’t uploaded anywhere.
  2. Click a field and type. Tick checkboxes and radio buttons, and pick options from drop-down lists. Fields where each letter goes in its own box, as used for ID numbers, are filled one character per box.
  3. If a field appears more than once in the form, such as your name on every page, typing it once fills every copy.
  4. Choose whether to Flatten (lock the answers so they can’t be edited). Leave it off if you or someone else still needs to change an answer.
  5. Download the filled PDF.

Filling in a form that has no fields

  1. Open Edit PDF and choose the form.
  2. Add a text box over each blank and type your answer. Change the size so the text fits the line.
  3. To tick a box, type an X in a small text box over it.
  4. If the form has old answers or printed text you need to cover, use a white-out box first, then type on top.

Signing the form

Once the answers are in, open the filled PDF in Sign PDF to draw, type or upload your signature and place it on the signature line. You can add the date and your initials the same way. Our guide to electronic and digital signatures explains when a typed or drawn signature is accepted.

Before you send it

  • Check every page, including pages you didn’t expect to fill in.
  • Flatten it if the answers shouldn’t change. Flatten PDF locks the answers and your signature into the page, so they show the same in every viewer; see how to flatten a PDF.
  • Keep a copy of exactly what you submitted.
  • Check the size limit of the upload form, and use Compress PDF if it’s too big.

US tax forms

For the most common IRS forms there are ready-to-fill pages with line-by-line instructions: Form W-9, Form W-4 and Form 1099-NEC.