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PDF Form Field Types Explained: Text, Checkbox, More
Interactive PDF forms are built from a small set of field types. Knowing what each one does explains why a form behaves the way it does — and which ones Fill PDF Forms can complete.
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Text fields
A text field accepts typed text. Variations include single-line and multi-line fields, fields with a maximum length, and comb fields that spread characters into evenly spaced cells. A field can also be marked required or read-only. Fill PDF Forms fills text fields, including multi-line ones.
Checkboxes
A checkbox is either on or off. Each checkbox has an on-value stored in the file, which is what a receiving system reads. Fill PDF Forms ticks and unticks checkboxes.
Radio buttons
Radio buttons come in groups where choosing one clears the others, such as “Married / Single / Divorced”. Every button in a group shares one field, and each button has its own export value. Fill PDF Forms selects one option in a group.
Dropdowns and list boxes
A dropdown (combo box) shows one choice at a time and expands to reveal the rest. A list box shows several rows at once and may allow more than one selection. A dropdown can also be editable, letting a user type a value that is not listed. Some fields store one value for what you see and a different value for what the form exports; the tool works with the visible option labels.
Fields Fill PDF Forms does not edit
- Signature fields: these are for digital signing, which this tool does not do.
- Push buttons: these trigger actions such as printing or resetting, which do not run here.
- Read-only fields: the form’s author has locked them.
- XFA forms: a different, legacy format that is not supported.
Calculated and scripted fields
Some forms compute totals or validate input with scripts. Those scripts do not run in Fill PDF Forms, so a total that a viewer would update automatically is not recalculated. Check calculated values yourself before sending the form.
PDF Form Field Types FAQ
- What is the difference between a dropdown and a list box?
- A dropdown shows one selected value in a compact box and opens to show the choices. A list box displays several choices at once and can allow multiple selections.
- Why can I tick only one radio button?
- Radio buttons in a group are mutually exclusive by design. If you need to allow several answers, the form should use checkboxes.
- What does “required” mean on a field?
- The form’s author marked it as necessary. Fill PDF Forms warns you if required fields are blank but still lets you download.
- Why does a field limit my text?
- The field has a maximum length set by the form. Text over the limit is rejected rather than cut off silently.
- Can a form field hold formatted text?
- Some forms use rich-text fields, which are not supported here. Standard plain-text fields are.
Related guides
- How to Fill Out a PDF FormFill in the interactive fields of a PDF form in your browser and download the completed, still-editable form — with the steps, what is saved, and what to check before you send it.
- Why a PDF Form Isn't FillableThe difference between flat forms, interactive AcroForms and XFA forms, how to tell which you have, and the practical options when a PDF form has no fields to type into.
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