PrincePDF 🚀

A Fast, Modern, and Minimalist PDF Viewer for Windows 11

PrincePDF is an ultra-responsive, lightweight PDF viewer written in Python with PyQt6 and PyMuPDF (MuPDF C++ engine). It is designed to deliver fluid 60+ FPS navigation, crisp High-DPI typography, modern Windows 11 Fluent dark and light styling, and seamless integration as your default system PDF reader.

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✨ Key Features

• ⚡ Instant Rendering & High Performance: Powered by native PyMuPDF C++ rasterization with smart LRU page and thumbnail memory caching. Only visible pages plus neighboring buffer pages are rendered in high resolution.
• 📐 Multiple View Modes:
  • Single Page View: Focus on one page at a time with instant keyboard/wheel page-flipping.
  • Continuous Scroll View: Smooth vertical reading flow with automatic page tracking.
  • Side-by-Side (Spread) View: Two-page book/manual spread view.
• 🔍 Smooth Zooming:
  • Dynamic Zoom (10% to 800%) with Ctrl + Mouse Wheel, Ctrl + +, Ctrl + -.
  • Fit to Width (Ctrl + 2) and Fit to Page (Ctrl + 1).
  • Pre-calibrated zoom dropdown (50%, 75%, 100%, 125%, 150%, 200%, 300%, 400%).
• 📋 Native Text Selection & Copy:
  • Click and drag over text with standard semi-transparent blue highlights.
  • Double-click to select a word, triple-click to select a line, or Ctrl + A to select all text on the current page.
  • Right-click context menu or Ctrl + C to copy formatted text to the Windows clipboard.
• 🔎 In-Document Search (Ctrl + F):
  • Floating search bar with real-time match counter (3 of 24).
  • Next (Enter / F3) and Previous (Shift + Enter / Shift + F3) match navigation.
  • On-page highlighting (bright yellow with vivid orange active match).
  • Search results panel in the sidebar with page badges and contextual text snippets.
• 🌙 Night Reading Mode (Ctrl + N):
  • High-speed color inversion inverting white backgrounds to dark for eye-friendly nighttime reading.
• 🌓 Modern Fluent UI Themes:
  • Windows 11 Dark Mode and Light Mode with a 1-click switcher.
  • Minimalist toolbar with crisp iconography, clean tooltips, and page jump box.
• 📑 Collapsible Sidebar (F4):
  • Page Thumbnails: Visual gallery of all pages with active page highlight.
  • Document Outline / Bookmarks: Interactive table of contents tree view.
  • Search Results: List of matching pages and excerpts.
• 🖨️ Print & Export:
  • Native Windows printing dialog with page ranges (Ctrl + P).
  • "Save As..." to export copies (Ctrl + S).
• 🪟 Windows 11 Default PDF Viewer Integration:
  • Registers PrincePDF.Document ProgID and .pdf file association in HKCU without requiring administrator privileges.
  • Seamlessly appears in Windows 11 Default Apps (ms-settings:defaultapps) and "Open With" menus.
  • Generates desktop shortcuts and silent windowless launchers (pythonw.exe).
  • Drag and drop any .pdf directly onto the viewer.

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⌨️ Keyboard Shortcuts Reference

Action	Shortcut
Open File	Ctrl + O
Save As	Ctrl + S
Print Document	Ctrl + P
Close Document	Ctrl + W
Copy Selected Text	Ctrl + C
Select All on Page	Ctrl + A
Find in Page	Ctrl + F
Find Next / Previous	Enter / Shift + Enter
Next Page	Page Down / Down Arrow / Right Arrow / Space
Previous Page	Page Up / Up Arrow / Left Arrow / Shift + Space
First / Last Page	Home / End
Go to Page Dialog	Ctrl + G
Single Page View	Ctrl + Alt + 1
Continuous Scroll	Ctrl + Alt + 2
Side-by-Side (Spread)	Ctrl + Alt + 3
Zoom In / Zoom Out	Ctrl + + / Ctrl + - (or Ctrl + Wheel)
Actual Size (100%)	Ctrl + 0
Fit to Page	Ctrl + 1
Fit to Width	Ctrl + 2
Rotate Clockwise	Ctrl + R
Night Reading Mode	Ctrl + N
Toggle Sidebar	F4
Fullscreen Mode	F11 (or Esc to exit)
Document Properties	Ctrl + D

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🛠️ How to Set as Default PDF Viewer in Windows 11

1. Open PrincePDF (or run PrincePDF.exe) and go to Tools → Set as Windows 11 Default PDF Viewer...
2. Click ① Register & Open Windows 11 Default Apps Settings (this automatically registers PrincePDF.exe with Windows 11).
3. In the Windows Settings search box, type .pdf (or PrincePDF).
4. Click on .pdf and select PrincePDF as your default app.
5. Direct Explorer Method: Right-click any .pdf file in Windows Explorer, select Open with → Choose another app → choose PrincePDF (or click Choose an app on your PC and select PrincePDF.exe) → select "Always".

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📁 Project Architecture

PrincePDF/
├── PrincePDF.exe            # Standalone single-file Windows 11 executable (85 MB)
├── main.py                  # Entry point, High-DPI setup, AppUserModelID, CLI args
├── viewer_window.py         # Main window, menus, modern toolbar, status bar
├── pdf_view_widget.py       # Core viewer: Single, Continuous, Side-by-Side views
├── page_widget.py           # Individual page: vector text selection, copy, search hits
├── sidebar_widget.py        # Collapsible sidebar: Thumbnails, Outline, Search hits
├── search_bar.py            # Floating / inline search control with match count
├── document_model.py        # PyMuPDF document interface, text, search, metadata
├── render_cache.py          # LRU memory cache, pixmap rendering, night mode inversion
├── windows_integration.py   # Registry file associations, Default Apps, desktop shortcut
├── app_config.py            # Settings persistence (~/.princepdf_config.json)
├── style.py                 # Modern Fluent-inspired Dark and Light stylesheets
├── dialogs.py               # Document properties, Go to page, Default app, About
├── resources/
│   ├── app_icon.ico         # Multi-resolution (16 to 256px) Windows icon
│   ├── app_icon.png         # 1024x1024 master supersampled PNG
│   ├── app_icon_512.png     # 512x512 High-DPI icon
│   └── app_icon_256.png     # 256x256 High-DPI icon
├── PrincePDF.bat            # Quick command-line launcher
├── PrincePDF.vbs            # Silent background launcher (no command window)
├── sample_document.pdf      # Test document with multi-page text & outline
└── test_viewer.py           # Automated test suite (14 test cases)

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🚀 Running PrincePDF

Direct Executable (Recommended for Windows 11):

Double-click:

PrincePDF.exe

Or open a PDF with the executable from command line:

.\PrincePDF.exe "sample_document.pdf"

From Python Source:

python main.py "sample_document.pdf"

Or silently without console window:

pythonw main.py

To run the automated test suite:

python test_viewer.py