Guide to Merging PDF Files in Python Using PyPDF2

In today's digital world, managing PDF documents efficiently is crucial, especially when dealing with multiple files that need to be consolidated. If you often work with PDFs and find yourself merging documents manually, this guide will show you how to automate that task using Python.

In this tutorial, we’ll create a Python script that merges multiple PDF files from a folder into a single PDF document, all while ensuring that the files are sorted alphabetically and numerically. By the end of this guide, you'll have a working solution that simplifies the process of merging PDFs in just a few steps.

Key Libraries Used:

1. os: For interacting with the file system and retrieving file paths.
2. PyPDF2 (PdfMerger): For merging multiple PDFs into one.
3. re: For sorting the file names both alphabetically and numerically using regular expressions.

Step 1: Installation of Required Libraries

Before we start coding, we need to install the necessary libraries. We will use the PyPDF2 library to handle PDF files. Follow these steps to install the required packages:

1. Install Python (If not already installed)

Make sure Python is installed on your system. You can download it from the official Python website. To check if Python is installed, open a terminal and run:

python --version

2. Install PyPDF2

To handle PDF merging, install the PyPDF2 library using pip, Python’s package manager. Open your terminal or command prompt and run the following command: 

pip install PyPDF2

This will install the library necessary to merge PDF files.

Step 2: Import the Necessary Libraries

Once the libraries are installed, the first step is to import the essential modules that enable file listing, sorting, and merging. We use the os module to navigate the file system, re for sorting logic, and PdfMerger from the PyPDF2 library to handle the PDF merging.

import os
from PyPDF2 import PdfMerger
import re
 

Step 3: Define a Function to List PDF Files

We create a function list_pdf_files() that accepts a folder path as input, retrieves all .pdf files, and sorts them both alphabetically and numerically. The sorting function ensures that files like file1.pdf, file2.pdf, and file10.pdf are sorted properly.

def list_pdf_files(folder):
    """List all .pdf files in the given folder, sorted alphabetically and numerically."""
    def alphanum_key(file):
        """Sort by numbers if present in the file name, otherwise alphabetically."""
        return [int(s) if s.isdigit() else s.lower() for s in re.split(r'(\d+)', file)]
    
    pdf_files = [f for f in os.listdir(folder) if f.endswith('.pdf')]
    return sorted(pdf_files, key=alphanum_key)

Step 4: Define the Merge Function

This is the core of the script, which handles the merging process. The function asks for the folder path containing the PDF files, lists and sorts them, confirms whether the user wants to proceed, and finally merges the files into one.

def merge_pdfs():
    try:
        # Step 1: Ask for the folder containing PDF files
        source_folder = input("Enter the folder path containing PDF files: ").strip()
        if not os.path.exists(source_folder):
            print(f"The folder '{source_folder}' does not exist.")
            return
        
        # Step 2: List all PDF files in the source folder, sorted alphabetically
        pdf_files = list_pdf_files(source_folder)
        if not pdf_files:
            print(f"No PDF files found in the folder '{source_folder}'.")
            return
        
        print("The following PDF files were found (sorted alphabetically):")
        for i, pdf_file in enumerate(pdf_files, start=1):
            print(f"{i}. {pdf_file}")
        
        # Step 3: Ask for confirmation to proceed
        proceed = input("Do you want to proceed with merging these files into one PDF? (yes/no): ").strip().lower()
        if proceed != 'yes':
            print("Merging aborted.")
            return
        
        # Step 4: Merge all PDFs into one file in alphabetical order
        merger = PdfMerger()
        for pdf_file in pdf_files:
            pdf_path = os.path.join(source_folder, pdf_file)
            print(f"Merging '{pdf_file}'...")
            merger.append(pdf_path)
        
        # Step 5: Save the merged PDF to a new file
        output_pdf_path = os.path.join(source_folder, "merged_output.pdf")
        merger.write(output_pdf_path)
        merger.close()
        
        print(f"All files merged into: {output_pdf_path}")
    
    except Exception as e:
        print(f"An error occurred during the process: {e}")

Step 5: Run the Script

The final part of the script is the execution. We simply call the merge_pdfs() function, which will prompt the user for input and handle the entire merging process.

# Run the PDF merger
merge_pdfs()

How It Works:

• The user provides the folder path containing the PDF files.
• The script lists all the .pdf files, sorts them alphabetically and numerically.
• The user is asked whether they want to proceed with merging the files.
• The script merges all the PDFs in the folder and saves the final file as merged_output.pdf in the same directory.

Key Features:

• Alphabetical and Numerical Sorting: The script intelligently sorts files by name and number, ensuring that files with numeric suffixes like report1.pdf and report2.pdf appear in the correct order
• User Interaction: The user is asked to confirm the merging operation, which prevents accidental merges.
• Error Handling: If something goes wrong (e.g., an invalid file path), the script provides a helpful error message.

Conclusion

With this simple Python script, you can easily merge multiple PDF files into one without the hassle of manually arranging them. Whether you’re working with reports, research papers, or any other type of document, this tool offers a quick and efficient way to handle your PDF management needs. By following the steps outlined in this guide, you’ll be able to create your own PDF merger in Python. The script is flexible and can be easily modified or extended for additional functionalities, such as filtering specific PDFs or adding metadata to the final merged document.

Happy coding!