How to Fill Out a PDF Form Online for Free

Plenty of PDF forms -- job applications, intake forms, government paperwork -- come with real fillable fields built in, but filling them out has historically meant owning Acrobat or creating an account somewhere. LockerPDF's Fill PDF Form tool fills text fields, checkboxes, dropdowns, and radio buttons directly in your browser, with no signup and no upload.

What kind of PDF this works with

This is the detail that matters most before you start: the tool fills in fields that already exist in the PDF. It works with PDFs that contain a real AcroForm -- the underlying form-field data structure that PDF software like Acrobat, Word, or online form builders can create. It does not add new fields to a PDF that doesn't have any. If you upload a scanned form or a "flat" PDF with no fillable fields, the tool will tell you so directly rather than silently doing nothing: "This PDF doesn't have any fillable form fields." There's no workaround for that inside this tool -- if a form has no real fields, the fastest free options are printing and filling it by hand, or checking whether the issuer offers a fillable version.

How do you know ahead of time? If a PDF form has real fields, most PDF viewers will show input boxes, checkboxes, or highlighted click targets when you open it and click around -- that's the AcroForm data at work. If nothing responds to clicking and it just looks like a static page, it's a flat PDF.

Step by step: filling out a PDF form

1. Go to the Fill PDF Form tool and drag your PDF into the dropzone, or click to browse for it.
2. If the PDF has fillable fields, they're listed alongside a reference preview of the page, so you can see exactly what each field corresponds to. Use the page navigation and zoom controls to check the layout on longer forms, and the "Page N" jump button next to each field to see where it sits.
3. Fill in each field: type into text boxes (including multi-line ones), check checkboxes, pick an option from dropdowns, or select a radio button from each group.
4. Decide whether to flatten the form (see below), then click "Fill & Download."
5. Download filled.pdf.

The field types this tool supports

Four field types are supported: single-line and multi-line text fields, checkboxes, dropdown menus, and radio button groups -- covering the large majority of forms you'll encounter. Push buttons and list boxes aren't shown in the field list, since push buttons hold no fillable value and list boxes are uncommon enough that they aren't supported yet. If a form relies heavily on either of those, the fields you can fill will still show up normally, but those specific controls won't appear in the list.

Should you flatten the form?

There's a checkbox on the fill screen: "Flatten the form so filled values display correctly in every PDF viewer." It's checked by default, and it's worth understanding what it does before you decide whether to leave it that way.

Flattening burns the values you entered directly into the page content, permanently, so the form no longer behaves like a form afterward -- it just looks like a normal page with your answers printed on it. This guarantees your filled-in values display identically no matter what software someone opens the PDF in afterward, including older viewers or printers that sometimes render form fields inconsistently. The tradeoff is that the result is no longer editable as a form -- nobody, including you, can go back and change an answer through the form fields once it's flattened.

Leave the box unchecked if you want the PDF to stay editable -- for example, if you're filling in a draft version you expect to revise, or handing the file to someone else who needs to adjust an answer before submitting it. Check it (the default) when the form is final and you want it to look right everywhere, especially before printing or submitting to a system that might not render live form fields correctly.

Filling and signing together

Many forms need both: fields filled in and a signature at the bottom. Fill out the form fields first with this tool, download the result, then run that file through Sign PDF to draw, type, or upload a signature and place it on the page. Both tools run entirely client-side, so you can chain them without the document ever leaving your device at any point in the process. See this earlier post on signing a PDF online for free for the full walkthrough of that step.

Why this doesn't require uploading your form

Reading and writing AcroForm field values is, like most PDF operations, a matter of parsing and editing a well-defined file format -- it doesn't need server-side computation. LockerPDF reads your PDF's form structure, applies the values you typed, and optionally flattens them, all using JavaScript running in your browser tab. This matters for forms that often carry sensitive information -- names, addresses, ID numbers, medical or financial details -- since none of it is transmitted anywhere. You can verify this yourself: open your browser's developer tools (F12), switch to the Network tab, and fill out a form. No request will carry your document's data.

FAQ

Can this tool fill out any PDF, including scanned or flat forms?

No. It only fills fields that already exist in the PDF as a real AcroForm -- it can't detect blank areas on a scanned or flat PDF and turn them into fillable fields. If a PDF has no fillable fields, the tool tells you directly instead of silently doing nothing.

What field types can I fill in?

Text fields (including multi-line ones), checkboxes, dropdown menus, and radio button groups. Push buttons and list boxes aren't shown in the field list, since they either hold no fillable value or aren't common enough to support yet.

What does "flatten" do, and should I use it?

Flattening burns your entered values permanently into the page so they display identically in every PDF viewer and printer, but the form is no longer editable afterward. Leave it unchecked if you want the PDF to stay an editable form; leave it checked (the default) once the form is final.

Is my PDF uploaded anywhere when I fill it out?

No. The form is read, filled, and optionally flattened using JavaScript running in your browser -- your PDF is processed locally and never sent to a server. There's no account or signup required.