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PDF Tools API

Form Filler API

Populate PDF forms from application data, CRMs, onboarding flows, or internal systems and return a ready-to-send PDF.

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Credits

1 Credit / call

1 Credit per successful API request. Failed processing attempts are refunded automatically.

Pricing

1,000 Credits = $1

Every signed-in user receives 100 free API Credits each month.

Endpoint

/api/external/pdf-tools/form-filler

Use your API Key in the x-api-key header.

Use case

Use it when your product has structured data and a fillable PDF template, such as applications, onboarding packs, or approvals.

cURL example

curl -X POST https://itextmaster.com/api/external/pdf-tools/form-filler \
  -H 'x-api-key: YOUR_API_KEY' \
  -F 'file=@input.pdf;type=application/pdf' \
  -F 'options={"fields":{"Name":"Ada Lovelace","Approved":true},"flatten":true}' \
  --output filled-form.pdf

Multipart example

curl -X POST https://itextmaster.com/api/external/pdf-tools/form-filler \
  -H 'x-api-key: YOUR_API_KEY' \
  -F 'file=@input.pdf;type=application/pdf' \
  -F 'options={"fields":{"Name":"Ada Lovelace","Approved":true},"flatten":true}' \
  --output filled-form.pdf

JSON base64 example

curl -X POST https://itextmaster.com/api/external/pdf-tools/form-filler \
  -H 'Content-Type: application/json' \
  -H 'x-api-key: YOUR_API_KEY' \
  -d '{
    "file": { "name": "input.pdf", "dataBase64": "JVBERi0xLjcK..." },
    "options": {"fields":{"Name":"Ada Lovelace","Approved":true},"flatten":true}
  }' \
  --output filled-form.pdf

Node.js example

import { writeFile } from 'node:fs/promises';

const response = await fetch('https://itextmaster.com/api/external/pdf-tools/form-filler', {
  method: 'POST',
  headers: {
    'Content-Type': 'application/json',
    'x-api-key': process.env.ITEXTMASTER_API_KEY
  },
  body: JSON.stringify({
  file: { name: 'input.pdf', dataBase64: 'JVBERi0xLjcK...' },
  options: {"fields":{"Name":"Ada Lovelace","Approved":true},"flatten":true}
})
});

if (!response.ok) {
  throw new Error(await response.text());
}

await writeFile('filled-form.pdf', Buffer.from(await response.arrayBuffer()));

Python example

import os
import requests

response = requests.post(
    'https://itextmaster.com/api/external/pdf-tools/form-filler',
    headers={
        'Content-Type': 'application/json',
        'x-api-key': os.environ['ITEXTMASTER_API_KEY'],
    },
    json={
        'file': {'name': 'input.pdf', 'dataBase64': 'JVBERi0xLjcK...'},
        'options': {'fields': {'Name': 'Ada Lovelace', 'Approved': True}, 'flatten': True}
    },
)
response.raise_for_status()

with open('filled-form.pdf', 'wb') as f:
    f.write(response.content)

Error codes

401invalid_api_key

The x-api-key header is missing, invalid, or has been rotated.

402insufficient_credits

The account does not have enough API Credits for the request.

422pdf_tool_processing_failed

The file, options, or PDF structure could not be processed. Failed processing attempts are refunded automatically.

Limits

  • Works best with standard fillable PDF form fields.
  • Field names must match the source PDF field names.
  • Flattening makes fields static in the returned PDF.

Response headers

filled-form.pdf with X-Credits-Charged: 1 and X-Credit-Balance response headers.

Content-Type
The MIME type of the generated file, usually application/pdf or application/zip.
Content-Disposition
Attachment filename for the generated output.
X-Credits-Charged
Credits charged for the successful request.
X-Credit-Balance
Remaining API Credit balance after the request.

FAQ

How much does the Form Filler API cost?

Each successful Form Filler API request uses 1 Credit. 1,000 Credits cost $1, and every signed-in user receives 100 free API Credits each month.

What happens if processing fails?

Failed processing attempts are refunded automatically, and the API returns an error response you can log or retry.

Should I call this API from the browser?

No. Keep API Keys server-side and call the endpoint from your backend, queue, or automation job when you need to form filler.

Start with 100 free API Credits

Create an API Key, test Form Filler API, and buy more Credits only when automation volume grows.

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