PDF to PDF in Java

Overview

Merge, split and modify PDF documents with the PDFCrowd Java client. The client handles communication with the API, while processing runs on PDFCrowd's servers.

Installation

Add the Java client to the <dependencies> section of your pom.xml, or see other installation options.

<dependency>
  <groupId>com.pdfcrowd</groupId>
  <artifactId>pdfcrowd</artifactId>
  <version>6.7.0</version>
</dependency>

Quick Start

Update the input URLs and filenames as needed.

import com.pdfcrowd.Pdfcrowd;

class Example {
    public static void main(String[] args) throws Exception {
        Pdfcrowd.PdfToPdfClient client =
            new Pdfcrowd.PdfToPdfClient("demo", "demo");

        client.addPdfFile("cover.pdf");
        client.addPdfFile("proposal.pdf");
        client.addPdfFile("price.pdf");
        client.addPdfFile("contact.pdf");
        client.convertToFile("offer.pdf");
    }
}

import com.pdfcrowd.Pdfcrowd;

class Example {
    public static void main(String[] args) throws Exception {
        Pdfcrowd.PdfToPdfClient client =
            new Pdfcrowd.PdfToPdfClient("demo", "demo");

        client.setPageWatermark("watermark.pdf");
        client.addPdfFile("proposal.pdf");
        client.convertToFile("company_offer.pdf");
    }
}

import com.pdfcrowd.Pdfcrowd;

class Example {
    public static void main(String[] args) throws Exception {
        Pdfcrowd.PdfToPdfClient client =
            new Pdfcrowd.PdfToPdfClient("demo", "demo");

        client.setAction("extract");
        client.setPageRange("3,7-");
        client.addPdfFile("13_pages.pdf");
        client.convertToFile("output.pdf");
    }
}

Configure a Conversion

Authentication

Pass your PDFCrowd username and API key to PdfToPdfClient. Find your credentials on the API Keys page.

Add Input PDFs

Add each PDF before calling a conversion method. The default action joins the documents in the order they were added.

For encrypted input PDFs, set the document password with setInputPdfPassword() before conversion. This is separate from your API key and the passwords used to protect the output PDF.

Send PDF Bytes

Read two local PDFs as bytes, merge them in order, and save the result locally as merged.pdf:

import com.pdfcrowd.Pdfcrowd;
import java.nio.file.Files;
import java.nio.file.Path;

class Example {
    public static void main(String[] args) throws Exception {
        Pdfcrowd.PdfToPdfClient client =
            new Pdfcrowd.PdfToPdfClient("demo", "demo");

        client.addPdfRawData(Files.readAllBytes(Path.of("cover.pdf")));
        client.addPdfRawData(Files.readAllBytes(Path.of("proposal.pdf")));
        client.convertToFile("merged.pdf");
    }
}

Add Conversion Settings

Set conversion options on the client before calling a conversion method. For example, client.setLinearize(true); optimizes the output PDF for progressive loading.

Common settings are listed below. See the method reference for all available options or browse Java examples.

Use "extract" with a page range to keep selected pages, or "delete" to remove them. The "shuffle" action interleaves pages from the input PDFs.

Handle the Result

Choose an Output

After adding the inputs and settings, choose how to receive the PDF:

File-output methods overwrite an existing destination file.

This example merges two PDFs, receives the result as a byte[] and saves it as merged.pdf:

import com.pdfcrowd.Pdfcrowd;
import java.nio.file.Files;
import java.nio.file.Path;

class Example {
    public static void main(String[] args) throws Exception {
        Pdfcrowd.PdfToPdfClient client =
            new Pdfcrowd.PdfToPdfClient("demo", "demo");

        client.addPdfFile("cover.pdf");
        client.addPdfFile("proposal.pdf");
        byte[] result = client.convert();
        Files.write(Path.of("merged.pdf"), result);
    }
}

When serving the result from a web application, use Content-Type: application/pdf.

Handle Errors

The client throws a Pdfcrowd.Error exception on conversion or validation errors. This example merges two PDFs and logs any PDFCrowd error, including its HTTP status and reason code:

import com.pdfcrowd.Pdfcrowd;
import java.util.logging.Level;
import java.util.logging.Logger;

class Example {
    private static final Logger logger = Logger.getLogger(Example.class.getName());

    public static void main(String[] args) throws Exception {
        Pdfcrowd.PdfToPdfClient client =
            new Pdfcrowd.PdfToPdfClient("demo", "demo");

        try {
            client.addPdfFile("cover.pdf");
            client.addPdfFile("proposal.pdf");
            client.convertToFile("merged.pdf");
        } catch (Pdfcrowd.Error error) {
            logger.log(Level.SEVERE, "PDFCrowd conversion failed (status " +
                error.getStatusCode() + ", reason " + error.getReasonCode() + ")", error);
            throw error;
        }
    }
}

Local Java errors, such as a failure to read an input file or write the output, may need separate handling.

Pdfcrowd.Error provides these methods:

Common Status Codes

See all status and reason codes for specific explanations and Limits and Retries for retry behavior.

Read Conversion Information

This information is available after a conversion and describes the client's last conversion.

Limits and Retries

Request rate and concurrency limits depend on your license. Control how quickly your application submits conversions and how many it runs at once. A 429 response concerns request rate; a 430 response concerns requests already in progress. The maximum upload size is 300 MB.

The Java client automatically retries a request once when it receives HTTP 502 or 503. Use setRetryCount() to change that count, or set it to 0 to disable automatic retries. Account for these retries when adding an application-level retry policy.

Troubleshooting

Inspect a Conversion

This example merges two PDFs with debug logging enabled and logs the debug log URL when available. Use the input and settings from the conversion you are investigating.

import com.pdfcrowd.Pdfcrowd;
import java.util.logging.Level;
import java.util.logging.Logger;

class Example {
    private static final Logger logger = Logger.getLogger(Example.class.getName());

    public static void main(String[] args) throws Exception {
        Pdfcrowd.PdfToPdfClient client =
            new Pdfcrowd.PdfToPdfClient("demo", "demo");

        try {
            client.addPdfFile("cover.pdf");
            client.addPdfFile("proposal.pdf");
            client.setDebugLog(true);
            client.convertToFile("merged.pdf");
        } catch (Pdfcrowd.Error error) {
            logger.log(Level.SEVERE, "PDFCrowd conversion failed (status " +
                error.getStatusCode() + ", reason " + error.getReasonCode() + ")", error);
            throw error;
        } finally {
            String debugLogUrl = client.getDebugLogUrl();
            if (debugLogUrl != null && !debugLogUrl.isEmpty()) {
                logger.info("Debug log: " + debugLogUrl);
            }
        }
    }
}

The debug log contains conversion settings and processing details. You can also find logs in your conversion history. A local or connection failure may occur before a conversion log is available.

Common Problems

For help, contact support and include any available diagnostics, the client version, and enough detail to reproduce the problem.