Watermark

Stamp a text watermark on every page.

Request

POST https://api.bitaloka.io/v1/pdf/watermark

Multipart form→ application/pdf

Parameters

Name	Type	Description
`file`required	PDF file	The PDF to process (multipart file field).Example: `document.pdf`
`text`required	text	Watermark text drawn on every page.Example: `CONFIDENTIAL`

Code samples

Generated from one source and tested against the live API.

curl -sS -X POST "https://api.bitaloka.io/v1/pdf/watermark" \
  -H "X-API-Key: $BITALOKA_API_KEY" \
  -F "file=@document.pdf;type=application/pdf" \
  -F 'text=CONFIDENTIAL' \
  --fail-with-body -o watermarked.pdf

Uses: curl 7.x+ · example.sh

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

const apiKey = process.env.BITALOKA_API_KEY ?? ''

const form = new FormData()
form.append('file', await openAsBlob('document.pdf', { type: 'application/pdf' }), 'document.pdf')
form.append('text', "CONFIDENTIAL")

const res = await fetch("https://api.bitaloka.io/v1/pdf/watermark", {
  method: 'POST',
  headers: { 'X-API-Key': apiKey },
  body: form,
})
if (!res.ok) throw new Error(`HTTP ${res.status}: ${await res.text()}`)

await writeFile('watermarked.pdf', new Uint8Array(await res.arrayBuffer()))
console.log('Saved watermarked.pdf')

Uses: fetch · Node.js 20+ / browsers · example.mjs

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

const apiKey = process.env.BITALOKA_API_KEY ?? ''

const form = new FormData()
form.append('file', await openAsBlob('document.pdf', { type: 'application/pdf' }), 'document.pdf')
form.append('text', "CONFIDENTIAL")

const res = await fetch("https://api.bitaloka.io/v1/pdf/watermark", {
  method: 'POST',
  headers: { 'X-API-Key': apiKey },
  body: form,
})
if (!res.ok) throw new Error(`HTTP ${res.status}: ${await res.text()}`)

await writeFile('watermarked.pdf', new Uint8Array(await res.arrayBuffer()))
console.log('Saved watermarked.pdf')

Uses: fetch · Node.js 22+, Deno, Bun · example.mts

import os
from pathlib import Path

import requests

API_KEY = os.environ.get("BITALOKA_API_KEY", "")

res = requests.post(
    "https://api.bitaloka.io/v1/pdf/watermark",
    headers={"X-API-Key": API_KEY},
    files=[
        ("file", ("document.pdf", Path("document.pdf").read_bytes(), "application/pdf")),
    ],
    data={"text": "CONFIDENTIAL"},
    timeout=120,
)
res.raise_for_status()

Path("watermarked.pdf").write_bytes(res.content)
print("Saved watermarked.pdf")

Uses: requests · example.py

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.nio.file.Files;
import java.nio.file.Path;
import java.util.ArrayList;
import java.util.List;
import java.util.UUID;

public class Example {
    public static void main(String[] args) throws Exception {
        var client = HttpClient.newHttpClient();
        var apiKey = System.getenv().getOrDefault("BITALOKA_API_KEY", "");
        var boundary = "bitaloka-" + UUID.randomUUID();
        var body = new ArrayList<byte[]>();
        addFile(body, boundary, "file", Path.of("document.pdf"), "application/pdf");
        addField(body, boundary, "text", "CONFIDENTIAL");
        body.add(("--" + boundary + "--\r\n").getBytes(StandardCharsets.UTF_8));
        var request = HttpRequest.newBuilder(URI.create("https://api.bitaloka.io/v1/pdf/watermark"))
                .header("X-API-Key", apiKey)
                .header("Content-Type", "multipart/form-data; boundary=" + boundary)
                .POST(HttpRequest.BodyPublishers.ofByteArrays(body))
                .build();
        var response = client.send(request, HttpResponse.BodyHandlers.ofByteArray());
        if (response.statusCode() >= 400) {
            throw new RuntimeException("HTTP " + response.statusCode() + ": " + new String(response.body()));
        }
        Files.write(Path.of("watermarked.pdf"), response.body());
        System.out.println("Saved watermarked.pdf");
    }

    static void addField(List<byte[]> body, String boundary, String name, String value) {
        body.add(("--" + boundary + "\r\nContent-Disposition: form-data; name=\"" + name + "\"\r\n\r\n" + value + "\r\n").getBytes(StandardCharsets.UTF_8));
    }

    static void addFile(List<byte[]> body, String boundary, String name, Path file, String type) throws IOException {
        body.add(("--" + boundary + "\r\nContent-Disposition: form-data; name=\"" + name + "\"; filename=\"" + file.getFileName() + "\"\r\nContent-Type: " + type + "\r\n\r\n").getBytes(StandardCharsets.UTF_8));
        body.add(Files.readAllBytes(file));
        body.add("\r\n".getBytes(StandardCharsets.UTF_8));
    }
}

Uses: java.net.http · Java 17+ · Example.java

using var http = new HttpClient();
http.DefaultRequestHeaders.Add("X-API-Key", Environment.GetEnvironmentVariable("BITALOKA_API_KEY") ?? "");

using var form = new MultipartFormDataContent();
var file1 = new ByteArrayContent(await File.ReadAllBytesAsync("document.pdf"));
file1.Headers.ContentType = new("application/pdf");
form.Add(file1, "file", "document.pdf");
form.Add(new StringContent("CONFIDENTIAL"), "text");
var res = await http.PostAsync("https://api.bitaloka.io/v1/pdf/watermark", form);
if (!res.IsSuccessStatusCode)
    throw new HttpRequestException($"HTTP {(int)res.StatusCode}: {await res.Content.ReadAsStringAsync()}");

await File.WriteAllBytesAsync("watermarked.pdf", await res.Content.ReadAsByteArrayAsync());
Console.WriteLine("Saved watermarked.pdf");

Uses: HttpClient · .NET 8 · Program.cs

<?php

$ch = curl_init('https://api.bitaloka.io/v1/pdf/watermark');
curl_setopt_array($ch, [
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_HTTPHEADER => ['X-API-Key: ' . getenv('BITALOKA_API_KEY')],
    CURLOPT_POSTFIELDS => [
        'file' => new CURLFile('document.pdf', 'application/pdf'),
        'text' => 'CONFIDENTIAL',
    ],
]);
$body = curl_exec($ch);
$status = curl_getinfo($ch, CURLINFO_RESPONSE_CODE);
curl_close($ch);

if ($body === false || $status >= 400) {
    throw new RuntimeException("HTTP $status: $body");
}

file_put_contents('watermarked.pdf', $body);
echo "Saved watermarked.pdf\n";

Uses: ext-curl · PHP 8+ · example.php

package main

import (
	"bytes"
	"fmt"
	"io"
	"mime/multipart"
	"net/http"
	"net/textproto"
	"os"
	"path/filepath"
)

func main() {
	var buf bytes.Buffer
	w := multipart.NewWriter(&buf)
	check(addFile(w, "file", "document.pdf", "application/pdf"))
	check(w.WriteField("text", "CONFIDENTIAL"))
	check(w.Close())

	req, err := http.NewRequest("POST", "https://api.bitaloka.io/v1/pdf/watermark", &buf)
	check(err)
	req.Header.Set("X-API-Key", os.Getenv("BITALOKA_API_KEY"))
	req.Header.Set("Content-Type", w.FormDataContentType())

	res, err := http.DefaultClient.Do(req)
	check(err)
	defer res.Body.Close()
	body, err := io.ReadAll(res.Body)
	check(err)
	if res.StatusCode >= 400 {
		panic(fmt.Sprintf("HTTP %d: %s", res.StatusCode, body))
	}
	check(os.WriteFile("watermarked.pdf", body, 0o644))
	fmt.Println("Saved watermarked.pdf")
}

func addFile(w *multipart.Writer, field, path, contentType string) error {
	data, err := os.ReadFile(path)
	if err != nil {
		return err
	}
	h := make(textproto.MIMEHeader)
	h.Set("Content-Disposition", fmt.Sprintf(`form-data; name="%s"; filename="%s"`, field, filepath.Base(path)))
	h.Set("Content-Type", contentType)
	part, err := w.CreatePart(h)
	if err != nil {
		return err
	}
	_, err = part.Write(data)
	return err
}

func check(err error) {
	if err != nil {
		panic(err)
	}
}

Uses: net/http · Go 1.21+ · main.go

// build.gradle.kts: implementation("com.squareup.okhttp3:okhttp:4.12.0")
import java.io.File
import okhttp3.MediaType.Companion.toMediaType
import okhttp3.MultipartBody
import okhttp3.OkHttpClient
import okhttp3.Request
import okhttp3.RequestBody.Companion.asRequestBody

fun main() {
    val client = OkHttpClient()
    val body = MultipartBody.Builder()
        .setType(MultipartBody.FORM)
        .addFormDataPart("file", "document.pdf", File("document.pdf").asRequestBody("application/pdf".toMediaType()))
        .addFormDataPart("text", "CONFIDENTIAL")
        .build()
    val request = Request.Builder()
        .url("https://api.bitaloka.io/v1/pdf/watermark")
        .header("X-API-Key", System.getenv("BITALOKA_API_KEY") ?: "")
        .post(body)
        .build()

    client.newCall(request).execute().use { res ->
        check(res.isSuccessful) { "HTTP ${res.code}: ${res.body?.string()}" }
        File("watermarked.pdf").writeBytes(res.body!!.bytes())
        println("Saved watermarked.pdf")
    }
}

Uses: OkHttp 4 · Main.kt

import Foundation

var request = URLRequest(url: URL(string: "https://api.bitaloka.io/v1/pdf/watermark")!)
request.setValue(ProcessInfo.processInfo.environment["BITALOKA_API_KEY"] ?? "", forHTTPHeaderField: "X-API-Key")
request.httpMethod = "POST"

let boundary = "bitaloka-\(UUID().uuidString)"
var body = Data()

func addField(_ name: String, _ value: String) {
    body.append("--\(boundary)\r\nContent-Disposition: form-data; name=\"\(name)\"\r\n\r\n\(value)\r\n".data(using: .utf8)!)
}

func addFile(_ name: String, _ path: String, _ type: String) throws {
    let url = URL(fileURLWithPath: path)
    body.append("--\(boundary)\r\nContent-Disposition: form-data; name=\"\(name)\"; filename=\"\(url.lastPathComponent)\"\r\nContent-Type: \(type)\r\n\r\n".data(using: .utf8)!)
    body.append(try Data(contentsOf: url))
    body.append("\r\n".data(using: .utf8)!)
}

try addFile("file", "document.pdf", "application/pdf")
addField("text", "CONFIDENTIAL")
body.append("--\(boundary)--\r\n".data(using: .utf8)!)
request.setValue("multipart/form-data; boundary=\(boundary)", forHTTPHeaderField: "Content-Type")

let (data, response) = try await URLSession.shared.upload(for: request, from: body)
guard let http = response as? HTTPURLResponse, http.statusCode < 400 else {
    fatalError("Request failed: \(String(decoding: data, as: UTF8.self))")
}
try data.write(to: URL(fileURLWithPath: "watermarked.pdf"))
print("Saved watermarked.pdf")

Uses: URLSession · Swift 5.7+ · main.swift

// Cargo.toml: reqwest = { version = "0.12", features = ["blocking", "multipart"] }

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let api_key = std::env::var("BITALOKA_API_KEY").unwrap_or_default();
    let client = reqwest::blocking::Client::new();
    let form = reqwest::blocking::multipart::Form::new()
        .file("file", "document.pdf")?
        .text("text", "CONFIDENTIAL");
    let res = client
        .post("https://api.bitaloka.io/v1/pdf/watermark")
        .header("X-API-Key", api_key)
        .multipart(form)
        .send()?
        .error_for_status()?;
    std::fs::write("watermarked.pdf", res.bytes()?)?;
    println!("Saved watermarked.pdf");
    Ok(())
}

Uses: reqwest 0.12 (blocking) · main.rs

Response

Returns the processed file as application/pdf. The samples save it as watermarked.pdf.

Use from an AI agent

On the Bitaloka MCP server this service is the pdf_watermark tool. MCP server →

Related services

POSTPDF info Read page count, size and metadata of a PDF. POSTMerge PDF Combine multiple PDFs into one. POSTSplit PDF Split a PDF into one file per page.