PDF編集
A free browser-based PDF editor. Merge multiple PDFs, split/extract pages, convert images to PDF, rotate pages, and add page numbers. All processing happens locally in your browser - files are never sent to external servers. Safe for confidential documents. Available instantly without registration.
PDF結合・分割・並び替え・回転・ページ番号追加・画像→PDF変換を1つのツールで。完全ブラウザ内処理で安全・無料。
What You Can Do
The PDF Editor provides all essential PDF editing features in your browser: merge multiple PDFs, extract/split pages, convert images to PDF, and more. Perfect for consolidating contracts, extracting presentation slides, and converting scanned images to PDF. All processing happens in your browser—files are never uploaded to servers.
- 📎 Merge: Combine multiple PDFs into one file
- ✂️ Split: Extract specific pages or split into individual pages
- 🖼️ Image to PDF: Convert JPG, PNG, WebP images to PDF
- 🔄 Rotate: Adjust page orientation by 90°/180°/270°
- 🔢 Page Numbers: Add page numbers to each page
📎 PDF Merge
Combine multiple PDF files into one
✂️ PDF Split
Split PDF into multiple files
🖼️ Image to PDF Conversion
Convert JPG, PNG, and other images to PDF
🔄 PDF Rotation
Rotate PDF pages
🔢 Add Page Numbers
Add page numbers to each page of the PDF
💡 Use Cases
- Merge: Consolidate contracts or invoices into one PDF
- Split: Extract and share only the pages you need
- Image→PDF: Convert receipts or scanned images to PDF
- Rotate: Fix pages with incorrect orientation from scanning
- Page Numbers: Add numbering to presentations or handouts
❓ Frequently Asked Questions
A. No, all processing is done in your browser. Files are never sent to servers and are processed entirely on your computer, ensuring complete safety.
A. PDFs up to several tens of MB can be processed without issues. However, very large files (over 100MB) may slow down your browser.
A. Currently, password-protected PDFs are not supported. Please remove the password before using this tool.
A. Merge, split, and rotate operations preserve the original PDF quality. Image-to-PDF conversion quality depends on the source image quality.
📚 Technical Guide to PDF Editing
📄 PDF Internal Structure and Merge/Split Mechanisms
PDF (Portable Document Format) is a document format developed by Adobe Systems, now standardized as ISO 32000. PDF files have the following internal structure:
🔹 Basic PDF File Structure
- Header: PDF version information (e.g.,
%PDF-1.7) - Body: Stores objects such as pages, fonts, and images
- Cross-reference table: Records file positions of each object
- Trailer: Document root information and cross-reference table location
🔹 How PDF Merging Works
When merging multiple PDFs, this tool performs the following operations:
- Parse each PDF: Load page objects, fonts, and images from each file
- Create new PDF document: Generate an empty PDF container
- Copy pages: Add pages from each PDF to the new PDF in order (including fonts and images)
- Rebuild cross-references: Recalculate object positions in the new file
- Generate final PDF: Write trailer and complete
🔹 How PDF Splitting Works
PDF splitting extracts only the specified pages:
- Parse source PDF: Load all pages and resources (fonts, images)
- Filter pages: Select only the user-specified page numbers
- Identify dependencies: Extract only the fonts and images used by selected pages
- Generate new PDF: Create a new PDF with only the required pages and resources
💡 This tool uses the JavaScript library "pdf-lib" to implement these operations. Both merging and splitting preserve the PDF's internal structure accurately, ensuring no quality degradation.
🔒 Security Benefits of Client-Side Processing
This tool performs all processing in your browser (client-side). This provides the following important security advantages:
🛡️ Confidential Document Safety
- No server upload required: PDF files are processed only on your computer and never sent over the internet
- Zero third-party access risk: Even PDFs containing contracts, invoices, or personal information cannot be viewed by anyone, including the site operator
- No logging: Filenames and access history are never recorded on servers
⚡ Performance and Privacy Combined
| Feature | Server-based | Browser-based (This Tool) |
|---|---|---|
| File Transfer | ❌ Server upload required | ✅ Local processing only |
| Processing Speed | ⚠️ Upload/download time required | ✅ No network latency |
| File Size Limit | ⚠️ Server-side limits (e.g., under 10MB) | ✅ Limited by browser memory (usually 100MB+ OK) |
| Confidential Documents | ❌ Risk of operator access | ✅ Completely private |
| Internet Connection | ❌ Required | ✅ Works offline after loading |
⚠️ When using online PDF editing tools, always verify they are "browser-based." Many free tools upload files to servers, creating risks of confidential document leaks.
⚙️ Technical Background of pdf-lib Library
This tool uses pdf-lib, an open-source JavaScript library.
🔹 pdf-lib Features
- Pure JavaScript implementation: Lightweight library with no dependencies, works in Node.js and browsers
- PDF specification compliant: Implementation based on ISO 32000-1 (PDF 1.7) specification
- Rich functionality: Add, delete, copy pages; draw text and images; manipulate forms
- Type-safe: Written in TypeScript, developer-friendly
🔹 Comparison with Alternative Libraries
| Library | Features | Use Case |
|---|---|---|
| pdf-lib | Lightweight, browser-based, editing-focused | ✅ Best for PDF merge/split |
| PDF.js (Mozilla) | Rendering-focused, limited editing | Best for PDF display/viewing |
| jsPDF | PDF generation only, cannot edit existing PDFs | Best for creating new PDFs |
| PDFKit | Node.js only, server-side processing | Backend PDF generation |
📌 pdf-lib is the most suitable library for editing existing PDFs (merge, split, rotate, etc.). Being browser-compatible enables secure PDF editing without servers.
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