Guide
How to Fill Out a PDF Form
How to fill in a PDF form online without Acrobat, what makes a PDF fillable in the first place, what to do when the fields will not accept typing, and whether to flatten before you send it.
TL;DR
- There are two kinds of PDF form, and which one you have decides everything: a fillable PDF with real interactive fields, or a flat PDF that is only a picture of a form.
- Fillable PDF: open it in Fill PDF Form, click the highlighted fields, type, and download. Runs in your browser, nothing uploaded.
- Flat or scanned form: there are no fields to fill, so use Edit PDF to place text anywhere on the page instead.
- Flatten before sending a final version — it bakes your answers into the page so the recipient cannot change them. Leave it off if someone else still needs to edit.
- If a form opens but refuses all typing, it is usually an XFA form from Adobe LiveCycle, which genuinely only works in Adobe Acrobat or Reader.
- Add a signature afterwards with Sign PDF, and a password with Protect PDF if the form contains personal data.
Filling in a PDF form should be simple, and often it is — click the box, type, done. When it is not, the reason is almost always the same: the file you were sent is not actually a form, or it is a form built in a format your software cannot open. This guide explains how to tell the difference in a few seconds, how to complete each kind, and what to do before you send the result back.
The Two Kinds of PDF Form
| Fillable (AcroForm) PDF | Flat PDF | |
|---|---|---|
| What it contains | Real interactive fields embedded in the file — text boxes, checkboxes, radio buttons, dropdowns | Only page content: text and lines, or a scanned image of a paper form |
| How to spot it | Clicking a blank shows a cursor, usually with a highlight on every field | Clicking does nothing; you can only select surrounding text, or nothing at all |
| How to fill it | Fill PDF Form — click and type | Edit PDF — place text boxes on the page |
| Where it comes from | Someone deliberately built the fields in Acrobat or a form designer | Exported flat, printed and scanned, or generated as a plain document |
No tool can fill a form that has no fields, because there is nothing to fill — this is a property of the file, not a limitation of the software. What a good tool can do is tell you so straight away, which saves the ten minutes usually spent assuming something is broken.
How to Fill a Fillable PDF — Step by Step
- 1
Open the Fill PDF Form tool
Go to Fill PDF Form on WeConvertIt. Everything happens in your browser, which matters when the form contains personal details.
- 2
Drop in your form
Drag the PDF onto the upload area. The tool renders each page and highlights every detected field. If it finds none, it tells you immediately so you can switch to Edit PDF.
- 3
Fill the fields
Click a text field to type, click a checkbox to tick it, pick from dropdowns and radio groups. Work through every page — long forms often have fields you have to scroll to reach.
- 4
Decide whether to flatten
Turn Flatten on to bake your answers permanently into the page. Leave it off to keep the fields interactive so someone else can still edit them.
- 5
Download the completed form
Click Download filled PDF. Your values are written into the real AcroForm fields with pdf-lib, so the file opens correctly in any standard viewer.
- 6
Sign or protect it if needed
Add a signature with Sign PDF, or encrypt the finished form with Protect PDF before emailing it.
Filling a Flat or Scanned Form
If the PDF is a scan or a flat export, switch to Edit PDF and add your answers as text placed on the page. A few things make the result look deliberate rather than improvised: match the font size to the surrounding print, position text just above the ruled line rather than sitting on it, and keep the size consistent across the whole document. For checkboxes, a typed X is clearer and more reliable than trying to draw a tick.
If the scan is skewed or hard to read, converting the pages to images with PDF to JPG and running them through Image to Text will at least give you the text content — useful when you need to quote the questions or check a reference number, though it does not make the form itself fillable.
Should You Flatten?
| Situation | Flatten? | Why |
|---|---|---|
| Submitting a completed application or claim | Yes | Answers become static page content that cannot be altered, and every viewer renders them identically. |
| Sending to a colleague who must add their section | No | The fields need to stay interactive so they can complete the rest. |
| Keeping a personal record of what you submitted | Yes | Guarantees the archived copy still shows your answers years later, whatever software you open it with. |
| Building a reusable template | No | Flattening is one-way — once the fields are removed, the template cannot be filled again. |
When the Form Refuses to Cooperate
- A message asking you to open the file in Adobe Reader means it is an XFA form, built with Adobe LiveCycle. XFA is an Adobe-specific XML format layered into a PDF wrapper, and Acrobat or Reader really is the only reliable way to complete one — this is a genuine limitation of every non-Adobe tool, including ours.
- Fields visible but uneditable usually indicates permission restrictions on an encrypted file. Unlock PDF clears them if you have the password.
- Values that vanish when you reopen the file mean the viewer displayed your typing without saving it. Download from the tool rather than saving a copy from a preview, and flatten to be certain.
- A form you filled once and need again should be kept unflattened as your master, with a flattened copy exported each time you submit.
Form Tools Compared
| Tool | Cost | Uploads your form? | Notes |
|---|---|---|---|
| Fill PDF Form (WeConvertIt) | Free, no account | No — runs in your browser | Fills AcroForm text fields, checkboxes, radio buttons, and dropdowns, with an optional flatten. Cannot open XFA forms. |
| Adobe Acrobat | Free Reader, paid Pro | No — desktop app | Reader fills standard and XFA forms for free. Pro additionally creates fillable fields, adds field validation, and manages distribution and response collection. |
| macOS Preview | Free, built in | No — local app | Fills standard AcroForm fields well and handles signatures neatly. No flatten option and no XFA support. |
| Smallpdf / DocHub / PDFescape | Free tier, then paid | Yes — server-side | Feature-rich and useful for collaboration, but a completed form is about the most sensitive document you can upload — worth weighing given what forms usually contain. |
After Filling the Form
Sign it if a signature is required, using Sign PDF. If the form has to go back alongside supporting documents, merge them into one file so the recipient gets a single attachment. If the combined file is too large for the submission portal, compress it — scanned attachments in particular shrink substantially. And because a completed form is usually full of personal data, adding a password before emailing it is a reasonable habit.
Frequently Asked Questions
How do I fill out a PDF form?
If the PDF has interactive fields, open it in Fill PDF Form, click each highlighted box to type, tick checkboxes, choose from dropdowns, and download the completed file. Your answers are written into the real form fields, so the result opens correctly in Acrobat, Preview, Chrome, or anything else. If the PDF has no fields, you need a different approach — see the section on flat forms below.
How do I fill out a PDF that is not fillable?
Use Edit PDF, which lets you place a text box anywhere on the page and type into it. This is the answer for scanned forms and for PDFs that were exported as flat documents: rather than filling fields that do not exist, you are adding new text on top of the page. It takes a little more care to line up with the printed lines, but the finished document looks the same to whoever receives it.
What is a fillable PDF?
A fillable PDF contains AcroForm fields — interactive elements embedded in the document, including text boxes, checkboxes, radio buttons, and dropdown menus. They are part of the file rather than drawn on the page, which is why a PDF viewer can highlight them and let you type. The form designer creates them in Acrobat or a similar tool; if nobody added them, the PDF is just a page and cannot be filled by any tool.
How do I know whether my PDF is fillable?
Open it in a PDF viewer and click where you would expect to type. If a cursor appears in a box, often with a light blue or grey highlight, the form is fillable. If clicking does nothing and you can only select the surrounding text, or if the whole page behaves like an image, it is a flat form. Fill PDF Form detects this for you immediately and says so rather than leaving you clicking hopefully.
How do I fill a PDF form without Adobe?
Use a browser-based filler such as Fill PDF Form, which reads the AcroForm fields and renders them as interactive inputs, then writes your values back into the PDF on download. macOS Preview also fills standard forms, as do Chrome and Firefox for simple ones. The one genuine exception is XFA forms, described below, which really do require Adobe software.
Why can I not type in my PDF form?
Three common reasons. The form may be flat, with no fields to type into — use Edit PDF instead. It may be password-protected with editing restricted, in which case Unlock PDF removes the protection if you have the password. Or it may be an XFA form built in Adobe LiveCycle, which most viewers cannot render at all and which typically shows a message asking you to open it in Adobe Reader.
Should I flatten a PDF form before sending it?
Flatten if you are submitting a final version. Flattening merges your answers into the page as static text and removes the fields, so the recipient sees exactly what you entered and cannot alter it, and it also avoids the occasional viewer that fails to display filled field values properly. Do not flatten if the form is being passed along for someone else to complete or amend, because the fields are gone for good once it is done.
How do I save a filled PDF form so the answers stay in it?
Download the completed file from the tool rather than printing to PDF or saving a copy from a preview. Some browser PDF viewers display your typing without actually storing it in the file, which is why a form can look filled on screen and arrive blank. Fill PDF Form writes values into the real fields with pdf-lib, and flattening gives you an extra guarantee that they are part of the page.
Is my filled form uploaded anywhere?
No. Rendering, field detection, filling, and final assembly all happen in your browser. This matters more for forms than for most documents, since a completed form usually contains exactly the information you would least want on someone else’s server — name, address, date of birth, bank details, medical history.