Android Java Project to Merge Multiple PDF Documents From Gallery Using iTextPDF Library

Welcome folks today in this blog post we will be seeing how to merge multiple pdf documents from gallery and save the merged one inside the external storage in android using the iTextPDF library in java. All the full source code of the application is shown below.

Get Started

In order to get started you need to make a new android project inside the android studio and then you will see the below directory structure as shown below at the end of the project.

Now first of all you need to go to build.gradle file and copy paste the below dependencies as shown below

build.gradle

dependencies {
    implementation 'com.itextpdf:itextpdf:5.5.13.2'
}

dependencies {

implementation 'com.itextpdf:itextpdf:5.5.13.2'

}

Now we need to edit the AndroidManifest.xml file and add the necessary permissions for saving the pdf document inside the external storage and also we need to add the provider tag as well as shown below

AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools">

    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

    <application
        android:allowBackup="true"
        android:dataExtractionRules="@xml/data_extraction_rules"
        android:fullBackupContent="@xml/backup_rules"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/Theme.DriveApp"
        tools:targetApi="31">
        <activity
            android:name=".MainActivity"
            android:exported="true">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

        <provider
            android:name="androidx.core.content.FileProvider"
            android:authorities="${applicationId}.provider"
            android:exported="false"
            android:grantUriPermissions="true">
            <meta-data
                android:name="android.support.FILE_PROVIDER_PATHS"
                android:resource="@xml/file_paths" />
        </provider>
    </application>

</manifest>

<?xml version="1.0" encoding="utf-8"?>

<manifest xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:tools="http://schemas.android.com/tools">

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

<application

android:allowBackup="true"

android:dataExtractionRules="@xml/data_extraction_rules"

android:fullBackupContent="@xml/backup_rules"

android:icon="@mipmap/ic_launcher"

android:label="@string/app_name"

android:supportsRtl="true"

android:theme="@style/Theme.DriveApp"

tools:targetApi="31">

<activity

android:name=".MainActivity"

android:exported="true">

<intent-filter>

</intent-filter>

</activity>

<provider

android:name="androidx.core.content.FileProvider"

android:authorities="${applicationId}.provider"

android:exported="false"

android:grantUriPermissions="true">

<meta-data

android:name="android.support.FILE_PROVIDER_PATHS"

android:resource="@xml/file_paths" />

</provider>

</application>

</manifest>

Here you need to replace your own package name and structure and now we need to create this file_paths.xml file inside the xml directory which holds the path where we will be saving the pdf documents.

xml/file_paths.xml

<?xml version="1.0" encoding="utf-8"?>
<paths xmlns:android="http://schemas.android.com/apk/res/android">
    <external-path
        name="external_files"
        path="." />
</paths>

<?xml version="1.0" encoding="utf-8"?>

<external-path

name="external_files"

path="." />

</paths>

Editing the Main Layout

Now we need to edit the activity_main.xml file for the project where we will have two buttons for selecting the pdf documents and also second one to merge the pdf documents into single one as shown below.

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/select_pdf_button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Select PDF files to merge" />
    

    <Button
        android:id="@+id/merge_pdf_button"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Merge PDF files" />

</LinearLayout>

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

xmlns:app="http://schemas.android.com/apk/res-auto"

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="match_parent"

android:layout_height="match_parent"

android:orientation="vertical"

tools:context=".MainActivity">

<Button

android:id="@+id/select_pdf_button"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="Select PDF files to merge" />

<Button

android:id="@+id/merge_pdf_button"

android:layout_width="match_parent"

android:layout_height="wrap_content"

android:text="Merge PDF files" />

</LinearLayout>

And now we need to edit the MainActivity.java file and copy paste the following code

MainActivity.java

package com.example.driveapp;

import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;
import androidx.core.content.FileProvider;

import com.itextpdf.text.Document;
import com.itextpdf.text.pdf.PdfCopy;
import com.itextpdf.text.pdf.PdfReader;

import java.io.File;
import java.io.FileOutputStream;
import java.util.ArrayList;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    private static final String TAG = "MainActivity";
    private static final int REQUEST_PICK_PDF_FILES = 1;

    private List<Uri> mSelectedPdfs = new ArrayList<>();

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button selectPdfButton = findViewById(R.id.select_pdf_button);
        selectPdfButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
                intent.setType("application/pdf");
                intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true);
                startActivityForResult(intent, REQUEST_PICK_PDF_FILES);
            }
        });

        Button mergePdfButton = findViewById(R.id.merge_pdf_button);
        mergePdfButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (mSelectedPdfs.isEmpty()) {
                    Toast.makeText(MainActivity.this, "Please select at least one PDF file", Toast.LENGTH_SHORT).show();
                    return;
                }
                try {
                    File mergedPdfFile = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOCUMENTS), "merged.pdf");
                    FileOutputStream outputStream = new FileOutputStream(mergedPdfFile);
                    Document document = new Document();
                    PdfCopy copy = new PdfCopy(document, outputStream);
                    document.open();
                    for (Uri pdfUri : mSelectedPdfs) {
                        PdfReader reader = new PdfReader(getContentResolver().openInputStream(pdfUri));
                        copy.addDocument(reader);
                        reader.close();
                    }
                    document.close();
                    outputStream.close();
                    Toast.makeText(MainActivity.this, "PDF files merged successfully", Toast.LENGTH_SHORT).show();
                    // Open the merged PDF file using a PDF viewer app
                    Intent intent = new Intent(Intent.ACTION_VIEW);
                    Uri fileUri = FileProvider.getUriForFile(MainActivity.this, BuildConfig.APPLICATION_ID + ".provider", mergedPdfFile);
                    intent.setDataAndType(fileUri, "application/pdf");
                    intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);
                    startActivity(intent);
                } catch (Exception e) {
                    Log.e(TAG, "Error while merging PDF files", e);
                    Toast.makeText(MainActivity.this, "Error while merging PDF files", Toast.LENGTH_SHORT).show();
                }
            }
        });
    }

    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == REQUEST_PICK_PDF_FILES && resultCode == RESULT_OK) {
            mSelectedPdfs.clear();
            if (data.getData() != null) {
                mSelectedPdfs.add(data.getData());
            } else if (data.getClipData() != null) {
                for (int i = 0; i < data.getClipData().getItemCount(); i++) {
                    mSelectedPdfs.add(data.getClipData().getItemAt(i).getUri());
                }
            }
            Toast.makeText(this, "Selected " + mSelectedPdfs.size() + " PDF files", Toast.LENGTH_SHORT).show();
        }
    }
}

package com.example.driveapp;

import android.content.Intent;

import android.net.Uri;

import android.os.Bundle;

import android.os.Environment;

import android.util.Log;

import android.view.View;

import android.widget.Button;

import android.widget.Toast;

import androidx.appcompat.app.AppCompatActivity;

import androidx.core.content.FileProvider;

import com.itextpdf.text.Document;

import com.itextpdf.text.pdf.PdfCopy;

import com.itextpdf.text.pdf.PdfReader;

import java.io.File;

import java.io.FileOutputStream;

import java.util.ArrayList;

import java.util.List;

public class MainActivity extends AppCompatActivity {

private static final String TAG = "MainActivity";

private static final int REQUEST_PICK_PDF_FILES = 1;

private List<Uri> mSelectedPdfs = new ArrayList<>();

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

Button selectPdfButton = findViewById(R.id.select_pdf_button);

selectPdfButton.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);

intent.setType("application/pdf");

intent.putExtra(Intent.EXTRA_ALLOW_MULTIPLE, true);

startActivityForResult(intent, REQUEST_PICK_PDF_FILES);

}

});

Button mergePdfButton = findViewById(R.id.merge_pdf_button);

mergePdfButton.setOnClickListener(new View.OnClickListener() {

@Override

public void onClick(View v) {

if (mSelectedPdfs.isEmpty()) {

Toast.makeText(MainActivity.this, "Please select at least one PDF file", Toast.LENGTH_SHORT).show();

return;

}

try {

File mergedPdfFile = new File(Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_DOCUMENTS), "merged.pdf");

FileOutputStream outputStream = new FileOutputStream(mergedPdfFile);

Document document = new Document();

PdfCopy copy = new PdfCopy(document, outputStream);

document.open();

for (Uri pdfUri : mSelectedPdfs) {

PdfReader reader = new PdfReader(getContentResolver().openInputStream(pdfUri));

copy.addDocument(reader);

reader.close();

}

document.close();

outputStream.close();

Toast.makeText(MainActivity.this, "PDF files merged successfully", Toast.LENGTH_SHORT).show();

// Open the merged PDF file using a PDF viewer app

Intent intent = new Intent(Intent.ACTION_VIEW);

Uri fileUri = FileProvider.getUriForFile(MainActivity.this, BuildConfig.APPLICATION_ID + ".provider", mergedPdfFile);

intent.setDataAndType(fileUri, "application/pdf");

intent.addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION);

startActivity(intent);

} catch (Exception e) {

Log.e(TAG, "Error while merging PDF files", e);

Toast.makeText(MainActivity.this, "Error while merging PDF files", Toast.LENGTH_SHORT).show();

}

});

}

@Override

protected void onActivityResult(int requestCode, int resultCode, Intent data) {

super.onActivityResult(requestCode, resultCode, data);

if (requestCode == REQUEST_PICK_PDF_FILES && resultCode == RESULT_OK) {

mSelectedPdfs.clear();

if (data.getData() != null) {

mSelectedPdfs.add(data.getData());

} else if (data.getClipData() != null) {

for (int i = 0; i < data.getClipData().getItemCount(); i++) {

mSelectedPdfs.add(data.getClipData().getItemAt(i).getUri());

}

Toast.makeText(this, "Selected " + mSelectedPdfs.size() + " PDF files", Toast.LENGTH_SHORT).show();

}

As you can see when we click the button to select the pdf documents we are opening the gallery of the user using the Intent class and then after selecting multiple pdf documents we are inserting all the pdf documents pages into one pdf document using the iTextPDF library as shown above. And after merging the pdf documents we are saving the output file inside the external directory called documents and then we are opening the resultant file inside the pdf viewer as shown below