📄 Custom PDF Generator for Question Papers

A lightweight, browserless REST API that generates print-ready PDF question papers from structured JSON data using PDFKit — ideal for educational platforms that require professional formatting without the overhead of headless browsers like Puppeteer.

🚀 Features

• 📘 Generates PDF directly from JSON using PDFKit
• 🧾 Structured two-column question format
• ✅ Supports multiple question types: MCQ, numerical, descriptive
• 📑 Separate sections for questions, answer key, and solutions
• ✏️ Clean and print-friendly layout
• ⚡ Fast and efficient (no browser required)
• 🖼️ Supports images, formulas (SVG), and custom logos/fonts

🛠️ Setup Instructions

📋 Prerequisites

• Node.js (v14 or higher)
• npm or yarn

📦 Installation

git clone https://github.com/Priom7/JSON-to-PDF-Generator.git
cd JSON-to-PDF-Generator

# Install dependencies
npm install

# Start the server
npm start

API will be available at:
http://localhost:3000/api/generate-pdf

📡 API Documentation

📍 Endpoint

POST /api/generate-pdf

Content-Type: application/json
Response: application/pdf

📥 Request Body Example

{
  "title": "Physics Examination Paper",
  "subject": "Physics",
  "date": "April 15, 2025",
  "duration": "3 hours",
  "totalMarks": 100,
  "instructions": [
    "All questions are compulsory",
    "There is no negative marking"
  ],
  "questions": [
    {
      "type": "mcq",
      "text": "A particle moves along the x-axis...",
      "options": ["300 J", "900 J", "1000 J", "3000 J"],
      "correctOption": 3,
      "solution": "Work done = ∫F(x)dx from x=0 to x=10..."
    }
  ]
}

✅ Success Response

• Status: 200 OK
• Content-Type: application/pdf
• Body: Binary PDF file

❌ Error Responses

• 400 Bad Request – Invalid JSON
• 500 Internal Server Error – PDF generation failed

📐 JSON Schema

| Field | Type | Description | | ------------- | ------------------ | ------------------------------------------ | | title | String | Title of the examination paper | | subject | String | Subject name | | date | String | Exam date | | duration | String | Exam duration (e.g., "3 hours") | | totalMarks | Number | Total marks | | instructions| Array<String> | Exam instructions | | questions | Array<Object> | List of questions |

🎯 Question Object

| Field | Type | Description | | -------------- | ------------------ | --------------------------------------------------------- | | type | String | "mcq", "numerical", or "descriptive" | | text | String | Question text | | options | Array<String> | (For MCQ) Answer options | | correctOption| Number | (For MCQ) Index of correct option | | answer | String | Correct answer (numerical/descriptive) | | solution | String | Detailed solution explanation | | images | Array<Object> | (Optional) Images with path, width, height, position |

🎨 Customization

🧱 Layout Configuration (pdfGenerator.js)

const CONFIG = {
  pageSize: 'A4',
  margin: { top: 50, bottom: 50, left: 40, right: 40 },
  columns: 2,
  columnGap: 20,
  fonts: {
    regular: 'Helvetica',
    bold: 'Helvetica-Bold',
    italic: 'Helvetica-Oblique'
  },
  fontSize: {
    title: 16,
    header: 12,
    subHeader: 10,
    normal: 10,
    small: 8
  }
};

🔡 Custom Fonts

1. Add your .ttf font files to a fonts/ directory.
2. Register them in pdfGenerator.js:

doc.registerFont('CustomFont', 'fonts/CustomFont.ttf');

Update config:

fonts: {
  regular: 'CustomFont',
  bold: 'CustomFont-Bold',
  italic: 'CustomFont-Italic'
}

🖼️ Logo Support

Include in JSON:

"logoPath": "path/to/logo.png"

🔢 Math & Image Support

• Simple Math: Unicode math characters
• Complex Math: Include <svg> in question text or integrate mathjax-node
• Images:

"images": [
  {
    "path": "path/to/image.png",
    "width": 300,
    "height": 200,
    "position": "center"
  }
]

📄 Page Numbering

Add to pdfGenerator.js:

doc.on('pageAdded', () => {
  const pageCount = doc.bufferedPageRange().count;
  doc.switchToPage(pageCount - 1);
  doc.fontSize(8)
     .text(`Page ${pageCount}`, doc.page.width / 2, doc.page.height - 20, { align: 'center' });
});

🐳 Docker Deployment

🧾 Dockerfile

FROM node:16-alpine

WORKDIR /usr/src/app

COPY package*.json ./
RUN npm install

COPY . .

EXPOSE 3000

CMD ["node", "server.js"]

📦 Build & Run

docker build -t pdf-generator .
docker run -p 3000:3000 pdf-generator

☁️ Cloud Deployment

AWS Elastic Beanstalk

eb init
eb create pdf-generator-env
eb deploy

Heroku

heroku create
git push heroku main

🧪 Test Script

Create sample-data.json, then run:

node test.js

test.js example:

const fs = require('fs');
const path = require('path');
const { generatePDF } = require('./pdfGenerator');

async function testPDFGeneration() {
  const dataPath = path.join(__dirname, 'sample-data.json');
  if (!fs.existsSync(dataPath)) return console.error('sample-data.json not found');

  const data = JSON.parse(fs.readFileSync(dataPath, 'utf8'));
  const pdf = await generatePDF(data);
  fs.writeFileSync('output-test.pdf', pdf);
  console.log('PDF generated → output-test.pdf');
}

testPDFGeneration().catch(console.error);

🛡️ Security & Optimization

• ✅ Input validation & sanitization
• 🔐 Add authentication for production
• ⏳ Use queues for batch requests
• 🧠 Add caching for templates
• 🚫 Rate limiting to prevent abuse

🐞 Troubleshooting

| Issue | Solution | | ------------------------------ | ------------------------------------------------------------- | | Large JSON payload | bodyParser.json({ limit: '50mb' }) | | Fonts not rendering | Ensure correct path and supported format (TTF/OTF) | | Images not displaying | Check file path and permissions | | Memory issues with large PDFs | Use streaming instead of buffering |

Enable debug logs:

DEBUG=true node server.js

🤝 Contributing

1. Fork the repo
2. Create a feature branch: git checkout -b feature/your-feature
3. Commit: git commit -m "Add your feature"
4. Push: git push origin feature/your-feature
5. Open a Pull Request 🚀