Add PDF Editor and Signer with intelligent detection and click-to-place

Author: RandyNorthrup

PDF Editor and Signer/README.md

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+# PDF Editor and Signer
+
+A sophisticated PDF editor with intelligent element detection, click-to-place text insertion, and digital signature capabilities built with PySide6 and PyMuPDF.
+
+## Features
+
+### Intelligent Element Detection
+- **Automatic Detection**: The application automatically detects interactive elements in your PDF:
+  - **Horizontal Lines**: Text fields and underlines (green highlight)
+  - **Signature Fields**: Areas with "signature" keywords (blue highlight)
+  - **Date Fields**: Areas with "date" keywords (red highlight)
+- **Visual Feedback**: Detected elements are highlighted when you hover nearby
+- **No Manual Controls**: Detection is always active - no buttons needed
+
+### Click-to-Place Text Insertion
+- **Smart Placement**: Click near any detected element (within 50 pixels) to add text
+- **Type-Aware Formatting**:
+  - Signature fields: Italic script font style
+  - Date fields: Auto-filled with current date (MM/DD/YYYY)
+  - Text lines: Standard font
+  - Freeform: Standard font anywhere on the page
+- **Auto-Focus**: Text boxes automatically receive focus when created
+- **Auto-Remove**: Empty text boxes disappear when you click away
+- **Intuitive UX**: Just click where you want to type - the app handles the rest
+
+### Selectable Text Overlay
+- **Native Selection**: Select and copy text directly from the PDF view
+- **Transparent Layer**: Text overlay doesn't interfere with visual appearance
+- **Preserved Layout**: Text positioned exactly as it appears in the PDF
+
+### Zoom Controls
+- **Zoom Slider**: 50% to 400% zoom range
+- **Zoom Buttons**: +/- buttons for incremental zoom (10% steps)
+- **Fit Width**: Automatically fit PDF to window width
+- **Fit Page**: Automatically fit entire page in view
+- **Zoom-Aware Coordinates**: Text placement accounts for current zoom level
+
+### Digital Signatures
+- **Certificate Management**:
+  - Create new certificates with RSA 2048-bit keys
+  - Load existing certificate and key files
+  - X.509 format with SHA-256 hashing
+- **PDF Signing**: Apply digital signatures to edited PDFs
+- **Signature Validation**: Digitally signed documents maintain integrity
+
+## Installation
+
+### Requirements
+- Python 3.7+
+- PySide6 (Qt6 GUI framework)
+- PyMuPDF (PDF rendering and manipulation)
+- pyHanko (digital signatures)
+- cryptography (certificate generation)
+
+### Install Dependencies
+
+```bash
+pip install -r requirements.txt
+```
+
+Or install individually:
+
+```bash
+pip install PySide6>=6.0.0 PyMuPDF>=1.23.0 pyHanko>=0.20.0 cryptography>=41.0.0
+```
+
+## Usage
+
+### Run the Application
+
+```bash
+python pdf_editor_signer.py
+```
+
+### Workflow
+
+1. **Open PDF**: Click "Open PDF" to load a document
+2. **Navigate**: Use page navigation controls or enter page number directly
+3. **Add Text**:
+   - Click near a detected line, signature field, or date field
+   - The text box appears automatically at the correct location
+   - Type your text (dates auto-fill)
+   - Click elsewhere when done (empty boxes disappear)
+4. **Zoom**: Use zoom controls to adjust view as needed
+5. **Select Text**: Select and copy text directly from the PDF
+6. **Save**: Click "Save PDF" to save your edits
+7. **Sign** (optional):
+   - Create or load a certificate
+   - Click "Sign PDF" to apply digital signature
+
+### Text Box Types
+
+The application automatically determines the text box type based on what you click:
+
+- **Text Line**: Click near a horizontal line (green highlight)
+- **Signature**: Click near a signature keyword (blue highlight)
+- **Date**: Click near a date keyword (red highlight)
+- **Freeform**: Click anywhere else on the page
+
+### Certificate Management
+
+**Create Certificate**:
+1. Click "Create Certificate"
+2. Enter details (Country, Organization, Common Name, etc.)
+3. Certificate and key files saved in current directory
+
+**Load Certificate**:
+1. Click "Load Certificate"
+2. Select certificate file (.pem)
+3. Select key file (.pem)
+4. Certificate loaded for signing
+
+## Architecture
+
+### Graphics System
+- **Z-Layering**:
+  - Z-Level -2: Selectable text overlay (transparent)
+  - Z-Level -1: Element detection highlights
+  - Z-Level 0: User-created text boxes
+- **Coordinate Conversion**: Automatic conversion between Qt scene coordinates and PDF coordinates
+
+### Detection Algorithm
+- **Line Detection**: Analyzes PDF drawings for horizontal rectangles (<5px height, >50px width)
+- **Text Pattern Matching**: Searches text blocks for "signature" and "date" keywords
+- **Distance Calculation**: Finds nearest detected element within 50-pixel threshold
+
+### Type Safety
+- Full type annotations throughout codebase
+- Strict mypy compliance
+- Qt type hints for all widgets and events
+
+## File Structure
+
+```
+PDF Editor and Signer/
+├── pdf_editor_signer.py    # Main application (~1200 lines)
+├── requirements.txt         # Python dependencies
+└── README.md               # This file
+```
+
+## Technical Details
+
+### Text Box Styling
+- **Signature**: `font-style: italic; font-family: 'Brush Script MT', cursive;`
+- **Date**: Auto-filled with current date on creation
+- **Standard**: Default font, adjustable size
+- **Border**: Yellow border for all editable boxes
+
+### PDF Manipulation
+- **Rendering**: PyMuPDF (fitz) converts pages to QPixmap
+- **Text Extraction**: `page.get_text("dict")` provides text with bounding boxes
+- **Drawing Detection**: `page.get_drawings()` provides vector graphics data
+- **Text Insertion**: Applied to PDF with zoom-aware coordinate conversion
+
+### Digital Signatures
+- **Key Algorithm**: RSA 2048-bit
+- **Certificate Format**: X.509
+- **Hash Algorithm**: SHA-256
+- **Signing Backend**: pyHanko with cryptography library
+
+## Known Limitations
+
+- Element detection works best with text-based PDFs (may not detect elements in scanned/image PDFs)
+- Signature detection requires text containing "signature" keyword
+- Date detection requires text containing "date" keyword
+- Custom detection patterns not currently configurable
+
+## Contributing
+
+Contributions welcome! Areas for enhancement:
+- OCR integration for scanned PDFs
+- Configurable detection patterns
+- Custom text box styles
+- Annotation tools (highlighting, shapes)
+- Form field recognition
+
+## License
+
+[Add your license here]
+
+## Credits
+
+Built with:
+- [PySide6](https://wiki.qt.io/Qt_for_Python) - Qt6 Python bindings
+- [PyMuPDF](https://pymupdf.readthedocs.io/) - PDF processing
+- [pyHanko](https://github.com/MatthiasValvekens/pyHanko) - PDF signing
+- [cryptography](https://cryptography.io/) - Cryptographic operations