Add Text to PDF Files with Java

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This tutorial shows you how to add text to PDF files from a Java application with the Add to PDF API Tool. The example builds a text_objects profile that controls placement and appearance before posting the PDF and instructions together. The walkthrough gives you a practical starting point that you can adapt when you need to add text to PDF files in your own document workflow.

Why Add Text to PDF Files with Java?

A case-management service may need to stamp a case number and review date onto an incoming document before it enters an approval queue. Adding text programmatically makes the identifier visible on the page and repeatable across every processed file.

The text_objects JSON array controls page number, coordinates, font, text size, color, opacity, rotation, and wrapping width. Coordinate values are expressed in PDF points.

Java Code Example

import io.github.cdimascio.dotenv.Dotenv;
import java.io.File;
import java.io.IOException;
import java.util.concurrent.TimeUnit;
import okhttp3.*;
import org.json.JSONObject;

public class PDFWithAddedText {

  // By default, we use the US-based API service. This is the primary endpoint for global use.
  private static final String API_URL = "https://api.pdfrest.com";

  // For GDPR compliance and enhanced performance for European users, you can switch to the EU-based
  // service by commenting out the URL above and uncommenting the URL below.
  // For more information visit https://pdfrest.com/pricing#how-do-eu-gdpr-api-calls-work
  // private static final String API_URL = "https://eu-api.pdfrest.com";

  // Specify the path to your file here, or as the first argument when running the program.
  private static final String DEFAULT_FILE_PATH = "/path/to/file";

  // Specify your API key here, or in the environment variable PDFREST_API_KEY.
  // You can also put the environment variable in a .env file.
  private static final String DEFAULT_API_KEY = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx";

  public static void main(String[] args) {
    File inputFile;
    if (args.length > 0) {
      inputFile = new File(args[0]);
    } else {
      inputFile = new File(DEFAULT_FILE_PATH);
    }

    final Dotenv dotenv = Dotenv.configure().ignoreIfMalformed().ignoreIfMissing().load();

    final String text_options =
        "[{\"font\":\"Times New Roman\",\"max_width\":\"175\",\"opacity\":\"1\",\"page\":\"1\",\"rotation\":\"0\",\"text\":\"sample text in PDF\",\"text_color_rgb\":\"0,0,0\",\"text_size\":\"30\",\"x\":\"72\",\"y\":\"144\"}]";
    final RequestBody inputFileRequestBody =
        RequestBody.create(inputFile, MediaType.parse("application/pdf"));
    RequestBody requestBody =
        new MultipartBody.Builder()
            .setType(MultipartBody.FORM)
            .addFormDataPart("file", inputFile.getName(), inputFileRequestBody)
            .addFormDataPart("text_objects", text_options)
            .addFormDataPart("output", "pdfrest_added_text")
            .build();
    Request request =
        new Request.Builder()
            .header("Api-Key", dotenv.get("PDFREST_API_KEY", DEFAULT_API_KEY))
            .url(API_URL + "/pdf-with-added-text")
            .post(requestBody)
            .build();
    try {
      OkHttpClient client =
          new OkHttpClient().newBuilder().readTimeout(60, TimeUnit.SECONDS).build();

      Response response = client.newCall(request).execute();
      System.out.println("Result code " + response.code());
      if (response.body() != null) {
        System.out.println(prettyJson(response.body().string()));
      }
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
  }

  private static String prettyJson(String json) {
    // https://stackoverflow.com/a/9583835/11996393
    return new JSONObject(json).toString(4);
  }
}

Source: Java sample on GitHub.

Breaking Down the Code

Load the Java HTTP and JSON dependencies

import io.github.cdimascio.dotenv.Dotenv;
import java.io.File;
import java.io.IOException;
import java.util.concurrent.TimeUnit;
import okhttp3.*;
import org.json.JSONObject;

This dependency set combines OkHttp networking with dotenv configuration and org.json processing.

Choose the input and load credentials

// service by commenting out the URL above and uncommenting the URL below.
  // For more information visit https://pdfrest.com/pricing#how-do-eu-gdpr-api-calls-work
  // private static final String API_URL = "https://eu-api.pdfrest.com";

  // Specify the path to your file here, or as the first argument when running the program.
  private static final String DEFAULT_FILE_PATH = "/path/to/file";

  // Specify your API key here, or in the environment variable PDFREST_API_KEY.
  // You can also put the environment variable in a .env file.
  private static final String DEFAULT_API_KEY = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx";

  public static void main(String[] args) {
    File inputFile;
    if (args.length > 0) {
      inputFile = new File(args[0]);
    } else {
      inputFile = new File(DEFAULT_FILE_PATH);
    }

    final Dotenv dotenv = Dotenv.configure().ignoreIfMalformed().ignoreIfMissing().load();

    final String text_options =

The startup code separates file selection from authentication so either value can change without rewriting the request.

Build the multipart request body

final RequestBody inputFileRequestBody =
        RequestBody.create(inputFile, MediaType.parse("application/pdf"));
    RequestBody requestBody =
        new MultipartBody.Builder()
            .setType(MultipartBody.FORM)
            .addFormDataPart("file", inputFile.getName(), inputFileRequestBody)
            .addFormDataPart("text_objects", text_options)
            .addFormDataPart("output", "pdfrest_added_text")
            .build();
    Request request =
        new Request.Builder()
            .header("Api-Key", dotenv.get("PDFREST_API_KEY", DEFAULT_API_KEY))
            .url(API_URL + "/pdf-with-added-text")
            .post(requestBody)
            .build();
    try {
      OkHttpClient client =

The text_objects JSON array controls page number, coordinates, font, text size, color, opacity, rotation, and wrapping width. Coordinate values are expressed in PDF points. The multipart section uses the form multipart type required for combining uploaded content with operation parameters.

Send the request to pdfRest

.build();
    Request request =
        new Request.Builder()
            .header("Api-Key", dotenv.get("PDFREST_API_KEY", DEFAULT_API_KEY))
            .url(API_URL + "/pdf-with-added-text")
            .post(requestBody)
            .build();
    try {
      OkHttpClient client =
          new OkHttpClient().newBuilder().readTimeout(60, TimeUnit.SECONDS).build();

The request builder adds the API key header, selects the operation URL, and attaches the prepared body; changing the base constant switches between US and EU service hosts.

Read the API response

OkHttpClient client =
          new OkHttpClient().newBuilder().readTimeout(60, TimeUnit.SECONDS).build();

      Response response = client.newCall(request).execute();
      System.out.println("Result code " + response.code());
      if (response.body() != null) {
        System.out.println(prettyJson(response.body().string()));
      }
    } catch (IOException e) {
      throw new RuntimeException(e);
    }
  }

  private static String prettyJson(String json) {
    // https://stackoverflow.com/a/9583835/11996393
    return new JSONObject(json).toString(4);

The response block shows the raw outcome for learning purposes; production code can retain output IDs and branch on reported errors.

Beyond the Tutorial

You have now seen how to add text to PDF files from a Java application. With that foundation, you can adapt the text-object array for document IDs, status labels, page-specific notices, or generated headings.

When you move beyond the sample, keep in mind that pDF coordinates are measured in points, so placement should be tested against the actual page dimensions and rotation of representative inputs. For variable text, calculate wrapping width and position from document data rather than assuming every identifier or notice occupies the same space.

You can experiment with the Add Text to PDF operation in API Lab. The Add to PDF API Tool documentation describes the full parameter and response contract.

Note: The Add Text to PDF example above uses multipart form data; to avoid transferring the same input again, compare the multipart call with the JSON payload example.

How to Add Text to PDF Files with Java