🔐 PDF Merger App

This application provides a robust, web-based graphical user interface (GUI) for merging multiple PDF files into a single document with advanced features. It is built using Python and the Streamlit framework.

✨ Key Features

• Easy File Upload: Upload multiple PDF files directly through the web interface.
• Custom Merge Order (Drag-and-Drop): Use the integrated sorter to manually rearrange the PDF files to define the exact merging sequence.
• Password Protection Removal: If a source PDF is password-protected, the app allows you to input the password, decrypt the file during processing, and merge its contents. The final merged output file will be unencrypted.
• Reliable Merging: Combines all successfully processed PDFs into one consolidated, clean file.
• Downloadable Output: Provides a direct button to download the merged PDF file.

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🚀 Installation and Setup

Follow these steps to set up and run the application locally on your machine.

1. Prerequisites

You must have Python 3.8+ installed on your system. It is highly recommended to use a virtual environment to manage dependencies.

2. Virtual Environment Setup

Activate your virtual environment (if you haven't already):

macOS/Linux:

python3 -m venv venv
source venv/bin/activate

Windows:

python -m venv venv
venv\Scripts\activate

3. Install Dependencies

Install all necessary Python libraries: Streamlit (for the GUI), PyPDF2 (for PDF manipulation), and streamlit-sortables (for drag-and-drop).

pip install streamlit PyPDF2 streamlit-sortables
or 
pip install -r requirements.txt

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💻 Usage

1. Save the Code

Save the Streamlit application code (the final version) into a file named pdf_merger_STVPW.py.

2. Run the App

With your virtual environment activated, run the Streamlit application from your terminal:

Bash

streamlit run pdf_merger_ST_VPW.py

3. Application Workflow

1. Upload Files: Click "1. Choose PDF files" to select your documents.
2. Input Passwords (Optional): If any file is protected, the app will generate an input field under "2. Password Input." Enter the correct password to allow the file to be decrypted and merged.
3. Reorder Files: Under "3. Drag-and-Drop to Reorder," click and drag the file names to arrange them in the desired merge sequence (top file comes first).
4. Merge: Click the "✨ Execute Merge" button.
5. Download: Once successful, click "⬇️ Download Merged PDF."

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⚠️ Troubleshooting a Common Error

If you see a ModuleNotFoundError despite having installed the libraries:

ModuleNotFoundError: No module named '...'

This means you are running the application using a Python interpreter outside of your activated virtual environment.

Solution: Ensure you execute the source venv/bin/activate (or Windows equivalent) command before running streamlit run .... Your terminal prompt must display (venv) to confirm activation.

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📦 Project Details

Libraries Used:

• streamlit: For creating the interactive web GUI.
• PyPDF2: For reading, decrypting, and merging the PDF files.
• streamlit-sortables: For enabling the user-friendly drag-and-drop functionality.
• io.BytesIO: For efficiently handling files in memory without saving them to the disk.