Fill PDF Forms handles PDFs that carry interactive fields (AcroForm): the text boxes, checkboxes, radio groups, dropdowns and multi-select lists in an application, registration or expense form are detected, ordered the way a person reads the pages, and you can either click a field on the page preview or work down the list on the right.

When you are done there are two ways out: “Keep interactive form” leaves the fields editable for the recipient, while “Flatten” fixes the values into the page. Field values can also be written to JSON and imported next time, which suits a form you fill again and again.

1. 01Detect the fieldsselecting the PDF makes the panel parse it and show “Fields (N in total, M modified)”; every field is labelled with its type (text, checkbox, radio, dropdown, list), whether it is read-only, and the page it sits on.
2. 02Fill it inclick “Fill on the page preview” and type in place, or edit directly in the list on the right. Text boxes respect the form's maximum length and multi-line settings.
3. 03Export or import JSON (optional)“Export JSON” produces <original-name>_form-data.json in the shape { field name: value }; “Import JSON” fills by field name and reports how many names were not found and therefore ignored.
4. 04Choose an export mode and download“Keep interactive form” → <original-name>_filled.pdf; “Flatten (fix content)” → <original-name>_flattened.pdf.

Accepted input

unencrypted PDFs with AcroForm fields; a file without fields shows “No form fields detected” — use “PDF Annotate” to add text instead

XFA

a file using an XFA dynamic form can only have its compatible standard fields handled, and the display may be incomplete

Field types

button fields need no filling; signature fields cannot be filled here (use “PDF Sign”), and read-only fields cannot be changed

Chinese font

values containing Chinese need the roughly 10 MB Noto Sans SC font from this site (first time), and fail when you are offline

What it does not do

it does not create a form in a PDF that has none, does not sign documents, and does not apply one JSON file to many files in a batch (import them one at a time)

Form parsing and filling run locally in the browser, and neither the PDF nor what you type is uploaded; Chinese values fetch a font file from this site once, and that request carries no document content.