One Open Source Project a Day (Part 53): PDF 补丁丁 - Full-Featured PDF Toolbox for Bookmarks, Restrictions, Merge/Split, OCR

Introduction

"Permanently free, never expires, no ads, no popups, no privacy snooping."

This is Part 53 of the "One Open Source Project a Day" series. Today's project is PDF 补丁丁 (PDFPatcher, GitHub).

Need to edit PDF bookmarks, remove copy/print restrictions, merge/split documents, extract images, or turn image-based PDFs into searchable bookmarks? PDF 补丁丁 is a PDF toolbox built on the .NET Framework: supports bookmark editing, page crop/rotate, restriction removal, extract/merge documents, structure exploration, OCR, font replacement, and more. Licensed under AGPL + Conscience License, permanently free, no ads, no popups.

What You'll Learn

PDFPatcher's core features and use cases
Technical architecture: iText + MuPDF dual-engine
Bookmark editor, document merge, OCR and other highlights
Meaning of the Conscience License
Comparison with similar PDF tools

Prerequisites

Basic understanding of PDF documents
Windows experience (tool is Windows-only)

Project Background

Project Overview

PDF 补丁丁 (PDFPatcher) is a PDF processing tool built with .NET Framework, using iText and MuPDF as core libraries. iText handles parsing, generation, modification, and font embedding; MuPDF handles PDF-to-bitmap rendering. Features cover editing, creation, split/merge, OCR, and structure analysis.

Author

Author: wmjordan
Repos: GitHub and Gitee
Website: pdfpatcher.cnblogs.com

Project Data

📄 License: AGPL + Conscience License
📦 Version: v1.1.0
🌐 Documentation: GitHub README, User Manual .docx
💬 Community: GitHub Issues

Core Features

Main Capabilities

Category	Features
Modify	Document properties, page numbers, links; unify page size; remove auto-open actions; remove copy/print restrictions; set reader initial mode; clean hidden junk; recompress B&W images; rotate pages
Bookmarks	Reading UI (vertical right-to-left); batch edit bookmark properties; precise bookmark positioning; find/replace (regex, XPath); auto-generate bookmarks
Create PDF	Merge PDFs or images; keep or add bookmarks; generate bookmarks from filenames; unify page size
Split/Merge	Split or merge PDFs, preserve or add bookmarks
Extract	High-speed lossless image export; pages to images; extract/delete pages; reorder pages
Advanced	Rename by metadata; OCR (Microsoft Office MODI); image PDF TOC to bookmarks; font replacement; embed fonts
Structure	Tree view of document structure; edit nodes; export to XML

Use Cases

Ebook organization: Merge scanned PDFs, generate bookmarks, unify page size
Remove restrictions: Remove copy/print limits for easier reading and citation
Batch processing: Rename by metadata, extract pages, batch export images
Image PDF optimization: OCR TOC pages into clickable bookmarks
Font embedding: Embed fonts to fix garbled text on Kindle and similar devices

Quick Start

Requirements:

Windows 7 or later
.NET Framework 4.0–4.8
OCR requires Microsoft Office 2003/2007 Document Imaging (MODI)

Download:

Get the latest release from GitHub Releases, extract and run — no installer.

Build from source (optional):

Visual Studio 2022 or newer
".NET desktop development" and "C++ desktop development" workloads
Target .NET Framework 4.8

Conscience License

AGPL + Conscience License: The software is under AGPL with an extra condition — "if the software helps you, do one good deed after each use." Deeds can be small; intention matters. If you build commercial software from the source and earn revenue, donate at least 0.1% to those in need. Compliance is a matter of conscience.

Project Advantages

Comparison	PDFPatcher	Commercial PDF Tools	Online PDF Tools
Cost	Permanently free	Subscription	Free/limited
Ads	None	None	Possible
Privacy	Local processing	Varies	Upload risk
Features	Edit, OCR, structure	Full-featured	Basic
Platform	Windows only	Multi-platform	Cross-platform

Deep Dive

Technical Architecture

Core components:

iText: .NET library for parsing, generating, modifying PDF, embedding TTF font subsets
MuPDF: C library for PDF-to-bitmap rendering, called via P/Invoke (SharpMuPDF)
JBig2: JBIG2 image encode/decode

Other components: ObjectListView, FreeImage, Cyotek ImageBox, TabControlExtra, HTMLRenderer, etc.

Source Structure

PDFPatcher/
├── App/              # Main application
│   ├── Common/       # Utilities
│   ├── Functions/    # UI and controls
│   ├── Lib/          # Third-party libs
│   ├── Model/        # Models
│   ├── Options/      # Options
│   └── Processor/    # PDF processing (incl. Mupdf P/Invoke)
├── JBig2/            # JBIG2 codec
├── doc/              # Documentation
└── 使用手册.docx

Feature Highlights

Bookmark editor: Regex and XPath support, quick selection of chapter/section bookmarks, auto-generation of document bookmarks.

OCR: Uses Microsoft Office MODI (Document Imaging) to recognize text in images and convert image PDF TOC pages into clickable bookmarks.

Font replacement and embedding: Replace document fonts; embed fonts into PDF to fix garbled text on devices like Kindle.

Project Links and Resources

Official Resources

🌟 GitHub: https://github.com/wmjordan/PDFPatcher
🌐 Gitee: https://gitee.com/wmjordan/pdfpatcher
📚 Documentation: README, User Manual .docx
💬 Issues: GitHub Issues

Target Audience

Ebook organization, scanned PDF handling
Users needing to remove PDF restrictions
Users needing batch merge, split, page extraction
Users needing OCR and font embedding
PDF format enthusiasts and developers

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