Radio Buttons in PDFs: How to Build a Proper Group Online for Free

You have an existing PDF and you want one clear choice per question. That means a radio button group, not checkboxes. This guide shows you how to add a radio group to an existing PDF online for free and get the behavior people expect: one selection, clean data — no upload required.

Radio vs. checkbox in one minute

Checkbox lets people select any number of items. You can try to simulate “only one” with naming tricks, but checkboxes can still end up all off. That is not what you want for a single-choice question.
Radio button enforces a single choice inside a group. Tap one, others in the same group turn off. That is exactly what you want for Title, Payment method, Delivery speed, and similar questions.

The anatomy of a radio group

Group name. Every radio in the same question must share the exact same name. That’s what ties them together into one set.
Choice value. Each radio in that set needs its own export value. The group’s data becomes the export value of the selected radio. When no option is selected, the internal value is Off.

Helpful to know:

Many editors auto-fill values like Choice1, Choice2. Rename them to meaningful values such as Standard, Express, Overnight.
Some tools support linking “in unison.” If two radio widgets share the same group name and the same choice value, selecting one will light up its twin elsewhere in the document. Handy if the same answer appears on two pages.

Step by step in fillPDF

Step 1: Open your PDF

Open the editor at /app/, click Load PDF, and set a comfortable zoom with + and −.

Step 2: Place the first radio

Choose Radiobox in the toolbar. Click where the first option belongs. Drag to nudge. Use the handle to size it so it sits neatly over the printed circle or bullet on the page.

Tip: Align the center of the widget with the printed marker. It makes the click target feel natural.

Step 3: Duplicate the rest

Select that radio and click Copy. Click to stamp a radio on each of the other options in the same question. When you are done, click Copy again or pick another tool to exit.

Step 4: Give the group a name

Select one radio. In the Properties bar, set Group to a short, clear name.
Examples: PaymentMethod, DeliverySpeed, Title

Now select the other radios for this question and give them the exact same group name. Same spelling, same case.

Step 5: Assign choice values

Give every option a distinct export value. Keep them short and unambiguous.

Examples for PaymentMethod:

Card
BankTransfer
Invoice

Examples for DeliverySpeed:

Standard
Express
Overnight

Step 6: Pick a default (optional)

If one option should be preselected, leave exactly one radio in the group turned on before you export. If you want the user to decide, make sure all start off.

Note: Radios are single-choice by design. Once a selection exists, most viewers will not let people clear the group to “no choice” unless you provide a visible “None” option.

Step 7: Test like a user

Only one option in the same group can be on at a time
Radios in different groups do not affect each other
Export the PDF and open it in your viewer to confirm the same behavior

Validation checklist

The group name is identical on every option in the question
Each option has a unique export value
The click target lines up with the printed text or bullet
Sample export shows the group name with the selected value
If nothing is selected, the internal value reads Off

Common mistakes and quick fixes

All radios toggle together across questions: Cause: you reused the same group name on different questions. Fix: give each question its own group name.
Two radios in one question can be on at once: Cause: one radio uses a different group name by mistake. Fix: standardize the group name.
Data shows Choice1 or Choice2: Cause: you left auto-generated values in place. Fix: rename export values to meaningful terms like Red, Blue, Green.
Radios seem “linked” in odd ways: Cause: duplicate name and duplicate choice value in places you didn’t mean to sync. Fix: keep the same name across a question, but only reuse the same choice value when you actually want unison behavior in multiple locations.
Tried to use checkboxes for a single-choice question: Symptom: people can tick none or several. Fix: use true radios. They enforce one-and-only-one.

Quick naming patterns you can reuse

Contact_Preference with values Email, Phone, Mail
Subscription_Term with values Monthly, Quarterly, Yearly
Order_PaymentMethod with values Card, BankTransfer, Invoice

Short, consistent names pay off when you export data or integrate with other systems.

Wrap up

A correct radio group is simple once you know the rules: same group name, unique choice values, one selection. Place the widgets cleanly, keep names consistent, and your PDF will behave the way people expect.

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