Building a Free Web-Based Document Converter with Scanner Support

Published: 3 days ago (December 2, 2025 at 02:45 AM EST)

3 min read

Source: Dev.to

Overview

In today’s digital world, we often need to convert, merge, and edit documents from various sources. Whether you’re working with PDFs, Word documents, images from your phone, or scanned documents from a physical scanner, having a unified tool that handles all these formats is invaluable.

Demo:
Free Online Document Converter with Scanner Support – Live Demo

Why This Tool Is Useful

Real-World Usage Scenarios

Home Office Document Management

Merge multiple scanned receipts into a single PDF for expense reports
Convert Word documents to PDF before submitting applications
Combine photos of handwritten notes with typed documents

Remote Work & Collaboration

Quickly edit and merge documents without uploading to cloud services (privacy‑focused)
Create document packages from mixed sources (camera, scanner, files)
Edit Word documents directly in the browser without Microsoft Office

Education

Students can merge lecture notes, screenshots, and scanned materials
Teachers can create combined study materials from various sources
No software installation required on school computers

Small Business

Process invoices and receipts from physical documents using a scanner
Create professional PDF portfolios from mixed media
Edit and merge contracts without expensive software

Key Advantages

100% Browser‑Based: No server uploads, no privacy concerns
Free Core Features: Document viewing, editing, merging, and export
Multi‑Format Support: PDF, Word, images, TIFF, text files
Physical Scanner Support: Optional integration with TWAIN/WIA/SANE/ICA scanners
Offline Capable: Works without internet after initial load

Free vs. Paid Features

Completely FREE Features (No License Required)

File upload and viewing (PDF, DOCX, images, TIFF, TXT)
Camera capture
Document editing (text and images)
Image editing (crop, rotate, filters, resize)
Drag‑and‑drop reordering
Merge documents
Export to PDF and Word
Undo/Redo
Thumbnail navigation
Zoom and pan

Scanner Integration

The Dynamic Web TWAIN trial license is required.

Technologies Overview

Library	Purpose
PDF.js	PDF rendering
Mammoth.js	DOCX to HTML conversion
jsPDF	PDF generation
html-docx-js	Word document generation
html2canvas	HTML to image rendering
UTIF.js	TIFF decoding
Dynamic Web TWAIN	Scanner integration

Step 1: HTML Structure

Create index.html with the basic structure:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document Reader & Editor</title>
    <link rel="stylesheet" href="style.css">
    <script src="lib/pdf.js"></script>
    <script>
        window.pdfjsLib.GlobalWorkerOptions.workerSrc = 'lib/pdf.worker.min.js';
    </script>
</head>
<body>
    <header>
        <h1>Document Converter & Gallery</h1>
        <p>Convert Word/PDF/Images, Merge, and Save.</p>
    </header>

    <!-- Controls -->
    <section id="controls">
        <button id="uploadBtn">Upload</button>
        <button id="cameraBtn">Camera</button>
        <button id="scannerBtn">Scanner</button>
        <!-- Additional controls -->
    </section>

    <!-- Thumbnails panel -->
    <aside id="thumbnails"></aside>

    <!-- Viewer panel -->
    <main id="viewer"></main>

    <!-- Loading overlay -->
    <div id="loadingOverlay">Processing Document...</div>
</body>
</html>

Key Elements

File input for uploading files
Camera button for capturing images
Scanner button for physical document scanning
Thumbnails panel for navigation
Viewer panel for displaying selected page
Loading overlay for feedback during DOCX processing

Step 2: CSS Styling

Create style.css for a modern, responsive interface:

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f4f7f9;
    color: #333;
    display: flex;
    flex-direction: column;
    height: 100vh;
    overflow: hidden;
}

header {
    background-color: #fff;
    border-bottom: 1px solid #dde3e8;
    padding: 20px 0;
    text-align: center;
}

header h1 {
    margin: 0;
    font-size: 1.8rem;
    color: #007bff;
}

/* Additional styling for controls, workspace, thumbnails, viewer, etc. */