Runs locally · Zero uploads

PDF Fill Form

Fill AcroForm fields, optionally flatten to lock them in.

Fields JSON (e.g. {"name":"Jane","date":"2026-04-07"})

Flatten after filling (lock fields)

How it works

Fill AcroForm PDF fields without uploading the document. Common workflow: tax forms, HR onboarding, e-signature prep. Provide field values as a JSON map of field name to value (string for text fields, boolean for checkboxes). Optionally flatten the form so the values become permanent.

Verify it yourself. Open DevTools → Network → run a conversion. The only requests you'll see are the page assets — your file never leaves this tab.

On mobile? Downloaded files save to your Files app (iPhone/iPad) or Downloads folder (Android). On iPhone, you can also check the Downloads button in Safari's toolbar. This is how all browser downloads work — not a Bytario limitation.

FAQ

How do I know what field names to use?

Open the PDF in Acrobat or the Bytario PDF Info tool to see the field list. Field names are case-sensitive.

What about XFA forms?

V1 supports AcroForm only — that covers about 95% of fillable PDFs in the wild. XFA (used by some legacy government forms) is not supported.

When should I flatten?

Flatten when sending the final document to someone who should not be able to edit the values. Skip flatten if the recipient needs to add more fields or change values.

Use via API

Need to automate this? The same engine is available as a REST API at api.bytario.com.

curl https://api.bytario.com/v1/pdf/fill-form \
  -H "Authorization: Bearer $BYTARIO_KEY" \
  -F "[email protected]" \
  -F 'fields={"name":"Jane","date":"2026-04-07"}' \
  -F "flatten=true" \
  --output filled.pdf

POST /v1/pdf/fill-form — full docs · pricing from $9/mo