Check a box in a PDF form, and handle radio buttons and dropdowns

By the getPDF team · Published 11 October 2026

The short answer

Open the form in the filler below and click the box: a checkbox ticks and clicks off again, a radio button picks one option of its group and releases the others, and a dropdown or list opens its options. The fields are tinted, so you see what can be clicked. If nothing reacts, the boxes are printed squares, not fields: put an X in each with Add text. Save, or save flattened so the answers cannot change.

Tick them now

Fill PDF formAcroForm fields, flatten or keep. Free, runs on your device.

Drop the form and the editor opens with Select active. A form shows a hint, “This file is a form: click a tinted field to fill it, Tab for the next one.” Everything runs on your device; nothing is uploaded.

What are the 4 kinds of choice fields?

Besides text fields, a PDF form has 4 kinds of fields that ask you to choose. They look alike on paper and behave differently.

The 4 choice fields of a PDF form, as the tinted fields look in the filler. The radio group is mid-choice: picking Self-employed releases Employed.

Field	What a click does	Can you clear it?
Checkbox	Ticks it; a second click clears it	Yes, click again
Radio button	Picks this option, releases the others in its group	No; pick another option, or Undo
Dropdown	Opens the form’s own list; you pick 1	Pick another option
List	Opens the options, plus “(none)”	Yes, pick “(none)”

The field names come from our rental application test form, which carries all 4. Hover over a field to see its label: the tooltip the form gives it, or a short form of its name.

How do I tick a checkbox?

Click the tinted square. It ticks.
Click again to clear it.
With the keyboard, Tab moves to the box without ticking it, and Space ticks or clears it. Shift+Tab goes back a field.

Checkboxes are independent: 3 boxes can all be on. The exception is a set of boxes the form’s author gave one shared name; they then act like radio buttons, and ticking one clears another. That is the form’s design, not a fault.

Why can’t I untick a radio button?

A radio group is built so that 1 option is on. Click Self-employed and Employed turns off; click Student and Self-employed turns off. Clicking the option that is already on does nothing. Once a group has an answer, a click cannot empty it.

In getPDF, Undo (Ctrl+Z) can, while the file is open. After a change it puts back the option that was on before; after the first choice in a group it leaves the group empty again, as the blank form had it. With the keyboard, Tab moves to a radio button without picking it, and Space picks it.

Click the dropdown and pick from the list. The list is the form’s own; getPDF shows exactly those options.

Some forms allow typing your own answer into a dropdown. The filler here offers only the list, so in such a field you cannot add a value of your own. Two honest routes:

Pick the nearest option, or leave the field empty, and put a short note next to it with Add text (for example “see note: Łódź”).
Fill that 1 field in an app that supports typed dropdown answers, such as Adobe Acrobat Reader, and do the rest wherever you like.

A list box (options laid open) takes 1 choice here. A list that allows several choices keeps the 1 you pick.

What about printed squares that do not react?

If a click on a square gives no tint and no tick, the form has no fields there. It is a flat form, a printout in PDF form.

Add text to PDFType anywhere, real searchable text. Free, runs on your device.

Pick Add text (T) in the editor.
Click inside the first square and type a capital X. Enter places it.
Set the size so the X sits inside the box; 10 to 11 pt fits most printed squares.
Select the X and drag it to centre it. Duplicate (Ctrl+D) makes the next one; drag it to its square.

The X is real text in the page, so it prints, copies and searches. For a whole form without fields, see fill a PDF form that has no fields.

Check your choices before you flatten

Read the page top to bottom and say only the chosen options aloud: “pets yes, self-employed, Graz, December.” Anything you did not mean to pick stands out.
Open the Changes list in the side panel: every tick and choice is a line there, so a box you ticked by mistake shows up. Undo takes it back.
Save, then Save flattened PDF for the copy you send. Flattened, the ticks are part of the page and cannot be clicked away. Keep the editable copy.

The honest part

How a field behaves is the form author’s decision. A radio group that cannot be cleared, checkboxes tied together, a dropdown without your answer: these behave the same in Acrobat, in a browser and here, because they are written into the file. getPDF does not add options to a dropdown, does not take typed answers in a dropdown, and does not create new fields yet. When a form is truly broken (a group where no option can be picked, a box that ticks the wrong one), the fix is a note on the page with Add text and a short word to whoever sent it. If the ticks vanish on the recipient’s side, see why a filled form shows blank.

Questions

How do I untick a radio button in a PDF form?

Not by clicking it: a radio group is built so exactly 1 option stays on once you pick one. In getPDF, Undo (Ctrl+Z) takes the choice back while the file is open: after a first choice the group is empty again, after a change the earlier option comes back.

Why does ticking one box untick another?

They are radio buttons, or checkboxes the form's author tied together under one name. Either way it is how the form was built, and every app behaves the same.

The dropdown does not have my answer. Can I type my own?

Some dropdowns allow typing, some do not; the author decides. getPDF offers only the dropdown's own list. When your answer is not there, pick the nearest option or leave it, and add a short text note beside the field.

The boxes are printed squares that do not react to a click. What now?

The form has no fields. Use Add text to put an X in each square, at a size that fits the box. It is real text in the file and prints like a tick.

Do my ticks show in Acrobat and on a phone?

Yes. The filler writes each box's state and its drawing, so viewers that respect the form show the same ticks. Save flattened when they must not change.