# Add an image watermark to a PDF

Stamp a PNG or JPEG image across the pages of a PDF, with control over transparency, margin, and which pages get it.

Add an image watermark to a PDF document. Supply a PNG or JPEG and control its
transparency and margin. By default the watermark is stamped on every page: use
the [`pages`](#selecting-pages) parameter to target a subset. The API is
stateless: your document is processed in-region and never stored.

## Endpoint

<Endpoint method="POST" path="/v1/add_image_watermark" />

Available in every region. See [Regions & data residency](/docs/api/regions-and-data-residency)
for routing and data residency.

| Region         | URL                                                 |
| -------------- | --------------------------------------------------- |
| Global         | `https://api.pdfblocks.com/v1/add_image_watermark`   |
| United States  | `https://us.api.pdfblocks.com/v1/add_image_watermark` |
| US HIPAA       | `https://hipaa.api.pdfblocks.com/v1/add_image_watermark` |
| European Union | `https://eu.api.pdfblocks.com/v1/add_image_watermark` |
| United Kingdom | `https://uk.api.pdfblocks.com/v1/add_image_watermark` |
| Canada         | `https://ca.api.pdfblocks.com/v1/add_image_watermark` |
| Australia      | `https://au.api.pdfblocks.com/v1/add_image_watermark` |
| Japan          | `https://jp.api.pdfblocks.com/v1/add_image_watermark` |
| India          | `https://in.api.pdfblocks.com/v1/add_image_watermark` |
| Brazil         | `https://br.api.pdfblocks.com/v1/add_image_watermark` |

## Authentication

Authenticate every request with your secret API key in the `X-API-Key` header,
over HTTPS. Create and manage keys from the
[dashboard](https://dashboard.pdfblocks.com). See
[Authentication](/docs/api/authentication) for details.

## Request

The endpoint accepts a `multipart/form-data` request body.

<ParamField name="file" type="file" required>
  The input PDF document.
</ParamField>

<ParamField name="image" type="file" required>
  The watermark image to stamp onto each page. Must be a PNG or JPEG. See
  [Working with files](/docs/api/working-with-files) for how to attach it.
</ParamField>

<ParamField name="transparency" type="integer" default="50">
  The transparency level, from `0` (fully opaque) to `100` (fully transparent).
</ParamField>

<ParamField name="margin" type="decimal" default="1.0">
  The distance, in inches, from the page border to the watermark. `0` or greater.
</ParamField>

<ParamField name="pages" type="string">
  The pages to stamp, written as a [page range](#selecting-pages) such as
  `1..3,5`. When omitted, the watermark is applied to every page. Maximum 1000
  characters.
</ParamField>

### Selecting pages

The `pages` parameter takes a comma-separated list of 1-based page numbers and
ranges. It is treated as a **set**: order and duplicates are ignored, and pages
are always stamped in document order.

| Pattern   | Selects                                    |
| --------- | ------------------------------------------ |
| *(omit)*  | Every page                                 |
| `1`       | The first page only                        |
| `1..3,5`  | Pages 1, 2, 3, and 5                       |
| `2..`     | Page 2 through the last page               |
| `..-2`    | The first page through the second-to-last  |
| `-1`      | The last page                              |

See [Selecting pages](/docs/api/selecting-pages) for the complete reference.

## Examples

Stamp a logo on every page at 60% transparency:

<CodeGroup>

```bash title="cURL"
curl https://api.pdfblocks.com/v1/add_image_watermark \
  -H 'X-API-Key: your_api_key' \
  -F file=@input.pdf \
  -F image=@logo.png \
  -F transparency=60 \
  -o watermarked.pdf
```

```python title="Python"
# pip install requests
import requests

with open('input.pdf', 'rb') as file, open('logo.png', 'rb') as image:
    response = requests.post(
        'https://api.pdfblocks.com/v1/add_image_watermark',
        headers={'X-API-Key': 'your_api_key'},
        files={'file': file, 'image': image},
        data={'transparency': 60},
    )

response.raise_for_status()
with open('watermarked.pdf', 'wb') as output:
    output.write(response.content)
```

```javascript title="Node.js"
// Node.js 18+
import { readFile, writeFile } from 'node:fs/promises';

const body = new FormData();
body.set('file', new Blob([await readFile('input.pdf')]), 'input.pdf');
body.set('image', new Blob([await readFile('logo.png')]), 'logo.png');
body.set('transparency', '60');

const response = await fetch('https://api.pdfblocks.com/v1/add_image_watermark', {
  method: 'POST',
  headers: { 'X-API-Key': 'your_api_key' },
  body,
});

if (!response.ok) throw new Error(`Request failed: ${response.status}`);
await writeFile('watermarked.pdf', Buffer.from(await response.arrayBuffer()));
```

```php title="PHP"
<?php
$ch = curl_init('https://api.pdfblocks.com/v1/add_image_watermark');
curl_setopt_array($ch, [
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => ['X-API-Key: your_api_key'],
    CURLOPT_POST => true,
    CURLOPT_POSTFIELDS => [
        'file' => new CURLFile('input.pdf', 'application/pdf'),
        'image' => new CURLFile('logo.png', 'image/png'),
        'transparency' => '60',
    ],
]);

$pdf = curl_exec($ch);
if (curl_getinfo($ch, CURLINFO_HTTP_CODE) === 200) {
    file_put_contents('watermarked.pdf', $pdf);
}
```

```ruby title="Ruby"
# gem install http
require 'http'

response = HTTP
  .headers('X-API-Key' => 'your_api_key')
  .post('https://api.pdfblocks.com/v1/add_image_watermark', form: {
    file: HTTP::FormData::File.new('input.pdf'),
    image: HTTP::FormData::File.new('logo.png'),
    transparency: '60',
  })

File.write('watermarked.pdf', response.body) if response.status.success?
```

```go title="Go"
package main

import (
	"bytes"
	"io"
	"mime/multipart"
	"net/http"
	"os"
)

func main() {
	var buf bytes.Buffer
	form := multipart.NewWriter(&buf)

	file, _ := os.Open("input.pdf")
	defer file.Close()
	filePart, _ := form.CreateFormFile("file", "input.pdf")
	io.Copy(filePart, file)

	image, _ := os.Open("logo.png")
	defer image.Close()
	imagePart, _ := form.CreateFormFile("image", "logo.png")
	io.Copy(imagePart, image)

	form.WriteField("transparency", "60")
	form.Close()

	req, _ := http.NewRequest("POST", "https://api.pdfblocks.com/v1/add_image_watermark", &buf)
	req.Header.Set("Content-Type", form.FormDataContentType())
	req.Header.Set("X-API-Key", "your_api_key")

	res, _ := http.DefaultClient.Do(req)
	defer res.Body.Close()

	out, _ := os.Create("watermarked.pdf")
	defer out.Close()
	io.Copy(out, res.Body)
}
```

```csharp title="C#"
using var client = new HttpClient();
client.DefaultRequestHeaders.Add("X-API-Key", "your_api_key");

using var form = new MultipartFormDataContent
{
    { new ByteArrayContent(File.ReadAllBytes("input.pdf")), "file", "input.pdf" },
    { new ByteArrayContent(File.ReadAllBytes("logo.png")), "image", "logo.png" },
    { new StringContent("60"), "transparency" },
};

var response = await client.PostAsync(
    "https://api.pdfblocks.com/v1/add_image_watermark", form);
response.EnsureSuccessStatusCode();
await File.WriteAllBytesAsync(
    "watermarked.pdf", await response.Content.ReadAsByteArrayAsync());
```

</CodeGroup>

## Response

On success, the response is `200 OK` with the watermarked PDF as the body:

```http
HTTP/1.1 200 OK
Content-Type: application/pdf
Content-Length: 51820
```

The output preserves the input's page count and dimensions: only the watermark
is added. Stream the body straight to a file, as the examples above do; nothing
is stored on our side.

## Errors

Failed requests return an `application/problem+json` body. The most common one
for this endpoint is a `400`, returned when a parameter is invalid or `image`
isn't a supported format. The `errors` object names each field:

```json
{
  "type": "https://www.pdfblocks.com/docs/api/v1/error/400",
  "title": "One or more validation errors occurred.",
  "status": 400,
  "errors": {
    "image": ["The image must be a PNG or JPEG file."]
  }
}
```

A missing or invalid `X-API-Key` returns a `401`. See
[Errors](/docs/api/errors) for every status code and the full response shape.

## Recipes

Common variations. Expand one to see it in every language.

<AccordionGroup>

<Accordion title="A faint logo on every page">

<CodeGroup>

```bash title="cURL"
curl https://api.pdfblocks.com/v1/add_image_watermark \
  -H 'X-API-Key: your_api_key' \
  -F file=@input.pdf \
  -F image=@logo.png \
  -F transparency=85 \
  -o faint.pdf
```

```python title="Python"
import requests

with open('input.pdf', 'rb') as file, open('logo.png', 'rb') as image:
    response = requests.post(
        'https://api.pdfblocks.com/v1/add_image_watermark',
        headers={'X-API-Key': 'your_api_key'},
        files={'file': file, 'image': image},
        data={'transparency': 85},
    )

response.raise_for_status()
with open('faint.pdf', 'wb') as output:
    output.write(response.content)
```

```javascript title="Node.js"
import { readFile, writeFile } from 'node:fs/promises';

const body = new FormData();
body.set('file', new Blob([await readFile('input.pdf')]), 'input.pdf');
body.set('image', new Blob([await readFile('logo.png')]), 'logo.png');
body.set('transparency', '85');

const response = await fetch('https://api.pdfblocks.com/v1/add_image_watermark', {
  method: 'POST',
  headers: { 'X-API-Key': 'your_api_key' },
  body,
});

if (!response.ok) throw new Error(`Request failed: ${response.status}`);
await writeFile('faint.pdf', Buffer.from(await response.arrayBuffer()));
```

```php title="PHP"
<?php
$ch = curl_init('https://api.pdfblocks.com/v1/add_image_watermark');
curl_setopt_array($ch, [
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => ['X-API-Key: your_api_key'],
    CURLOPT_POST => true,
    CURLOPT_POSTFIELDS => [
        'file' => new CURLFile('input.pdf', 'application/pdf'),
        'image' => new CURLFile('logo.png', 'image/png'),
        'transparency' => '85',
    ],
]);

$pdf = curl_exec($ch);
if (curl_getinfo($ch, CURLINFO_HTTP_CODE) === 200) {
    file_put_contents('faint.pdf', $pdf);
}
```

```ruby title="Ruby"
require 'http'

response = HTTP
  .headers('X-API-Key' => 'your_api_key')
  .post('https://api.pdfblocks.com/v1/add_image_watermark', form: {
    file: HTTP::FormData::File.new('input.pdf'),
    image: HTTP::FormData::File.new('logo.png'),
    transparency: '85',
  })

File.write('faint.pdf', response.body) if response.status.success?
```

```go title="Go"
package main

import (
	"bytes"
	"io"
	"mime/multipart"
	"net/http"
	"os"
)

func main() {
	var buf bytes.Buffer
	form := multipart.NewWriter(&buf)

	file, _ := os.Open("input.pdf")
	defer file.Close()
	filePart, _ := form.CreateFormFile("file", "input.pdf")
	io.Copy(filePart, file)

	image, _ := os.Open("logo.png")
	defer image.Close()
	imagePart, _ := form.CreateFormFile("image", "logo.png")
	io.Copy(imagePart, image)

	form.WriteField("transparency", "85")
	form.Close()

	req, _ := http.NewRequest("POST", "https://api.pdfblocks.com/v1/add_image_watermark", &buf)
	req.Header.Set("Content-Type", form.FormDataContentType())
	req.Header.Set("X-API-Key", "your_api_key")

	res, _ := http.DefaultClient.Do(req)
	defer res.Body.Close()

	out, _ := os.Create("faint.pdf")
	defer out.Close()
	io.Copy(out, res.Body)
}
```

```csharp title="C#"
using var client = new HttpClient();
client.DefaultRequestHeaders.Add("X-API-Key", "your_api_key");

using var form = new MultipartFormDataContent
{
    { new ByteArrayContent(File.ReadAllBytes("input.pdf")), "file", "input.pdf" },
    { new ByteArrayContent(File.ReadAllBytes("logo.png")), "image", "logo.png" },
    { new StringContent("85"), "transparency" },
};

var response = await client.PostAsync(
    "https://api.pdfblocks.com/v1/add_image_watermark", form);
response.EnsureSuccessStatusCode();
await File.WriteAllBytesAsync(
    "faint.pdf", await response.Content.ReadAsByteArrayAsync());
```

</CodeGroup>

</Accordion>

<Accordion title="A logo on the cover page only">

<CodeGroup>

```bash title="cURL"
curl https://api.pdfblocks.com/v1/add_image_watermark \
  -H 'X-API-Key: your_api_key' \
  -F file=@input.pdf \
  -F image=@logo.png \
  -F pages='1' \
  -o cover-stamped.pdf
```

```python title="Python"
import requests

with open('input.pdf', 'rb') as file, open('logo.png', 'rb') as image:
    response = requests.post(
        'https://api.pdfblocks.com/v1/add_image_watermark',
        headers={'X-API-Key': 'your_api_key'},
        files={'file': file, 'image': image},
        data={'pages': '1'},
    )

response.raise_for_status()
with open('cover-stamped.pdf', 'wb') as output:
    output.write(response.content)
```

```javascript title="Node.js"
import { readFile, writeFile } from 'node:fs/promises';

const body = new FormData();
body.set('file', new Blob([await readFile('input.pdf')]), 'input.pdf');
body.set('image', new Blob([await readFile('logo.png')]), 'logo.png');
body.set('pages', '1');

const response = await fetch('https://api.pdfblocks.com/v1/add_image_watermark', {
  method: 'POST',
  headers: { 'X-API-Key': 'your_api_key' },
  body,
});

if (!response.ok) throw new Error(`Request failed: ${response.status}`);
await writeFile('cover-stamped.pdf', Buffer.from(await response.arrayBuffer()));
```

```php title="PHP"
<?php
$ch = curl_init('https://api.pdfblocks.com/v1/add_image_watermark');
curl_setopt_array($ch, [
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => ['X-API-Key: your_api_key'],
    CURLOPT_POST => true,
    CURLOPT_POSTFIELDS => [
        'file' => new CURLFile('input.pdf', 'application/pdf'),
        'image' => new CURLFile('logo.png', 'image/png'),
        'pages' => '1',
    ],
]);

$pdf = curl_exec($ch);
if (curl_getinfo($ch, CURLINFO_HTTP_CODE) === 200) {
    file_put_contents('cover-stamped.pdf', $pdf);
}
```

```ruby title="Ruby"
require 'http'

response = HTTP
  .headers('X-API-Key' => 'your_api_key')
  .post('https://api.pdfblocks.com/v1/add_image_watermark', form: {
    file: HTTP::FormData::File.new('input.pdf'),
    image: HTTP::FormData::File.new('logo.png'),
    pages: '1',
  })

File.write('cover-stamped.pdf', response.body) if response.status.success?
```

```go title="Go"
package main

import (
	"bytes"
	"io"
	"mime/multipart"
	"net/http"
	"os"
)

func main() {
	var buf bytes.Buffer
	form := multipart.NewWriter(&buf)

	file, _ := os.Open("input.pdf")
	defer file.Close()
	filePart, _ := form.CreateFormFile("file", "input.pdf")
	io.Copy(filePart, file)

	image, _ := os.Open("logo.png")
	defer image.Close()
	imagePart, _ := form.CreateFormFile("image", "logo.png")
	io.Copy(imagePart, image)

	form.WriteField("pages", "1")
	form.Close()

	req, _ := http.NewRequest("POST", "https://api.pdfblocks.com/v1/add_image_watermark", &buf)
	req.Header.Set("Content-Type", form.FormDataContentType())
	req.Header.Set("X-API-Key", "your_api_key")

	res, _ := http.DefaultClient.Do(req)
	defer res.Body.Close()

	out, _ := os.Create("cover-stamped.pdf")
	defer out.Close()
	io.Copy(out, res.Body)
}
```

```csharp title="C#"
using var client = new HttpClient();
client.DefaultRequestHeaders.Add("X-API-Key", "your_api_key");

using var form = new MultipartFormDataContent
{
    { new ByteArrayContent(File.ReadAllBytes("input.pdf")), "file", "input.pdf" },
    { new ByteArrayContent(File.ReadAllBytes("logo.png")), "image", "logo.png" },
    { new StringContent("1"), "pages" },
};

var response = await client.PostAsync(
    "https://api.pdfblocks.com/v1/add_image_watermark", form);
response.EnsureSuccessStatusCode();
await File.WriteAllBytesAsync(
    "cover-stamped.pdf", await response.Content.ReadAsByteArrayAsync());
```

</CodeGroup>

</Accordion>

</AccordionGroup>

## Related actions

<CardGroup cols={2}>

<Card title="Add a text watermark" href="/docs/api/add-text-watermark-to-pdf">
  Stamp text instead of an image.
</Card>

<Card title="Add a password" href="/docs/api/add-password-to-pdf">
  Encrypt the watermarked document.
</Card>

<Card title="Merge documents" href="/docs/api/merge-pdf-documents">
  Combine files before watermarking.
</Card>

<Card title="Extract pages" href="/docs/api/extract-pages-from-pdf">
  Pull out the stamped pages.
</Card>

</CardGroup>