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PDF Tools API

Add Watermark API

Apply confidential, draft, approval, or brand watermarks to PDFs automatically before distribution or storage.

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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/add-watermark

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

Use case

Use it when every generated contract, policy, invoice, or review copy needs a visible status label before it leaves your system.

cURL example

curl -X POST https://itextmaster.com/api/external/pdf-tools/add-watermark \
  -H 'x-api-key: YOUR_API_KEY' \
  -F 'file=@input.pdf;type=application/pdf' \
  -F 'options={"type":"text","text":"CONFIDENTIAL","position":"diagonal","opacity":0.25,"fontSize":48}' \
  --output watermarked.pdf

Multipart example

curl -X POST https://itextmaster.com/api/external/pdf-tools/add-watermark \
  -H 'x-api-key: YOUR_API_KEY' \
  -F 'file=@input.pdf;type=application/pdf' \
  -F 'options={"type":"text","text":"CONFIDENTIAL","position":"diagonal","opacity":0.25,"fontSize":48}' \
  --output watermarked.pdf

JSON base64 example

curl -X POST https://itextmaster.com/api/external/pdf-tools/add-watermark \
  -H 'Content-Type: application/json' \
  -H 'x-api-key: YOUR_API_KEY' \
  -d '{
    "file": { "name": "input.pdf", "dataBase64": "JVBERi0xLjcK..." },
    "options": {"type":"text","text":"CONFIDENTIAL","position":"diagonal","opacity":0.25,"fontSize":48}
  }' \
  --output watermarked.pdf

Node.js example

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

const response = await fetch('https://itextmaster.com/api/external/pdf-tools/add-watermark', {
  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: {"type":"text","text":"CONFIDENTIAL","position":"diagonal","opacity":0.25,"fontSize":48}
})
});

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

await writeFile('watermarked.pdf', Buffer.from(await response.arrayBuffer()));

Python example

import os
import requests

response = requests.post(
    'https://itextmaster.com/api/external/pdf-tools/add-watermark',
    headers={
        'Content-Type': 'application/json',
        'x-api-key': os.environ['ITEXTMASTER_API_KEY'],
    },
    json={
        'file': {'name': 'input.pdf', 'dataBase64': 'JVBERi0xLjcK...'},
        'options': {'type': 'text', 'text': 'CONFIDENTIAL', 'position': 'diagonal', 'opacity': 0.25, 'fontSize': 48}
    },
)
response.raise_for_status()

with open('watermarked.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

  • Text watermarking is best for classification labels and simple branding.
  • Very complex transparency or page boxes may affect visual placement.
  • Preview with representative files before large batch runs.

Response headers

watermarked.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 Add Watermark API cost?

Each successful Add Watermark 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 add watermark.

Start with 100 free API Credits

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

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