# Fill and flatten PDF forms

> Browser-only file conversion. Selected files are processed on this device and are not uploaded to a conversion server.

Source: https://localconverter.tech/fill-pdf-form

Fill supported standard AcroForm fields by supplying a JSON object keyed by field name. Text, checkbox and single-choice fields are supported, with optional flattening for a less editable final copy. This is useful for repeatable form preparation when you know the actual field names and can review every completed value.

## Useful tasks

- Fill named text fields in a PDF form
- Set supported checkboxes using JSON booleans
- Flatten completed AcroForm fields into page content

## Steps

1. **Choose a standard PDF form**: Upload an unprotected PDF with standard AcroForm fields. A scanned blank form has no interactive fields to fill, and dynamic XFA forms are unsupported.
2. **Enter named JSON values**: Provide an object mapping field names to values, such as {"name":"Alex","approved":true}. Use JSON booleans for checkboxes and an available exact value for a choice field.
3. **Choose whether to flatten**: Enable Flatten fields when the completed widgets should become page content, or disable it to retain supported editable fields. Run Process document after checking the JSON syntax.
4. **Inspect every completed field**: Download the form and check names, choices and checkbox states in a PDF reader. If flattened, confirm the visible values are correct before using the completed document.

## Settings

- **Field values as JSON**: Field values as JSON is applied to this tool job. Use the syntax shown in the workflow, especially for JSON field mappings. The initial value is “{}”.
- **Flatten fields**: Turn “Flatten fields” on only when it matches your intended result. The initial state is on. Read the workflow and output limitations below when this changes how the original content is processed.

## A simple review form

A standard AcroForm contains name, department and approved fields. Enter a JSON object using those exact names and a boolean for approved. Keep flattening off for further review, then inspect the saved form’s text and checkbox state in a reader.

## Check the result

Choose a file, adjust the settings, then download the result. Standard AcroForm text, checkbox (JSON true/false) and single-choice fields. Dynamic XFA forms are rejected. Unknown field names fail with available names. Open the saved output in the app or workflow where you plan to use it. Check one representative result before repeating the same settings with more files. The original files stay unchanged.

## Limits

- Files are processed on this device. Browser memory and engine-specific limits apply. Save results before reloading.
- Standard AcroForm text, checkbox (JSON true/false) and single-choice fields. Dynamic XFA forms are rejected. Unknown field names fail with available names.
- Upload one file with a combined size of at most 100 MB. The completed output must fit within 200 MB.
- Files are checked by the local engine; a matching filename alone is not proof of valid contents.
- Selections and completed jobs stay available while you navigate inside this tab. Use My files to revisit results. Reloading or closing the tab clears the workspace; download results you want to keep first.

## Questions

### How do I find the actual field names?

Use the form’s authoring information when available. If you submit unknown field names, the tool returns an error with available names, which can help you correct the JSON keys rather than guessing from visible page labels.

### What values should checkboxes receive?

Checkbox fields require JSON true or false, without quotation marks. The tool maps those booleans to the field’s own checked or unchecked state, avoiding the need to guess internal PDF checkbox export values.

### What does flattening change?

Flattening turns supported completed form widgets into page content so they no longer behave as editable form fields. Review the values before using that copy, and retain the source if later form edits may be necessary.

### Can this fill XFA or scanned forms?

Dynamic XFA forms are rejected, and a scan without AcroForm widgets has no named fields for this operation. Use a suitable authoring workflow to create standard fields or prepare a visual overlay for those different document types.

### Does Fill and flatten PDF forms upload files to another service?

Processing runs in this browser, on your device. Files and pasted input are not uploaded to a conversion server. The website and required engine assets must load first; large operations depend on available device memory.

### Can I continue after changing pages?

Selections and completed jobs stay available while you navigate inside this tab. Use My files to revisit results. Reloading or closing the tab clears the workspace; download results you want to keep first.

## Related guides

- [Merge PDF](https://localconverter.tech/merge-pdf.md)
- [Split PDF](https://localconverter.tech/split-pdf.md)
- [Images to PDF](https://localconverter.tech/images-to-pdf.md)
- [Reorder PDF pages](https://localconverter.tech/reorder-pdf.md)
- [PDF to TXT](https://localconverter.tech/pdf-to-txt.md)
- [PDF to PNG](https://localconverter.tech/pdf-to-png.md)