Adding a text watermark in PHP with cURL

In this guide, we'll walk you through the process of adding text watermarks to your PDF files, using PDFShift's API.

Adding a watermark to your PDF can be done by adding the watermark object to your query. Adding a text allows you to customize its content and PDFShift's API provides a few properties to help you customize the visual aspect, such as the font size, color, and position.

# You can get an API key at https://pdfshift.io
$api_key = 'sk_xxxxxxxxxxxx'

$params = array (
    'source' => 'https://www.example.com',
    'watermark' => array (
        'text' => 'PROTECTED DOCUMENT',
        'offset_x' => 'center',
        'offset_top' => 'top'
    )
)

$curl = curl_init('https://api.pdfshift.io/v3/convert/pdf');
curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_POSTFIELDS, json_encode($params));
curl_setopt($curl, CURLOPT_HTTPHEADER, array(
    'Content-Type: application/json',
    'Authorization: Basic ' . base64_encode('api:' . $api_key)
));

$response = curl_exec($curl);
if ($response === false) {
    $error_message = curl_error($curl);
    curl_close($curl);
    throw new Exception("cURL error: $error_message");
}

// Get the HTTP status code
$http_status = curl_getinfo($curl, CURLINFO_HTTP_CODE);

// Close cURL resource
curl_close($curl);

// Check if the request was successful
if ($http_status !== 200) {
    throw new Exception("Request failed with HTTP status code: $http_status");
}

// Save the file to result.pdf
file_put_contents('result.pdf', $response);

echo 'The PDF document was generated and saved to result.pdf';

You can customize the text watermark by applying the following properties:

• font_size: The size of the text. An integer value in pixels. Defaults to 16.
• font_family : The font family to be used. Defaults to Helvetica.
• font_color : The color of the text. A hexadecimal color value. Defaults to '000000'.
• font_opacity : The opacity of the text. A float value between 0 and 100. Defaults to 100.
• font_bold: A boolean to set the text as bold. Defaults to false.
• font_italic: A boolean to set the text as italic. Defaults to false.

You can also customize the position of the text watermark by applying the following properties:

• offset_x: The horizontal position of the text. Can be 'left', 'center', 'right', or a specific value in pixels. Defaults to 'center'.
• offset_y: The vertical position of the text. Can be 'top', 'middle', 'bottom', or a specific value in pixels. Defaults to 'center'.

For the offset positions, we accept a value in integer which will be translated to pixels, but you can also pass a unit such as 'px', 'in', 'cm', 'mm', 'pt'.

For example:

$params = array (
    "source": "https://www.example.com",
    "watermark": {
        "text": "PROTECTED DOCUMENT",
        "offset_x": "5cm",
        "offset_top": "15mm"
    }
}