MJ PDF Reader: Fast & Free Android PDF Viewer

MJ PDF Reader is an open‑source Android PDF viewer designed for speed, simplicity, and reliability. Built with a clean, minimalist interface, it caters to users who require efficient local PDF viewing and effortless navigation without unnecessary clutter. The source code demonstrates modular architecture, using modern Android best practices and leveraging PDFium for rendering.

This Android app offers a high‑performance PDF engine capable of rendering complex documents with accuracy. Whether you’re working with text‑heavy files or graphics‑rich PDFs, MJ PDF Reader supports smooth zooming, quick page loading, and responsive pinch‑to‑zoom gestures. Developers can easily inspect the source code to understand how PDFium is integrated, and how view components are launched using Android’s native lifecycle and RecyclerView for list handling.

The repository places particular emphasis on modularity and maintainability. Key features include:

• Fast PDF rendering: The engine is powered by PDFium, ensuring high‑quality page layout and precise rendering.
• Minimal, modern UI: Built with simplicity in mind, using Android Jetpack components—activities, fragments, RecyclerView, and ConstraintLayout—for ease of use and navigation.
• Local filesystem support: Automatically detects and displays PDFs stored on internal or external storage, making it easy for users to access documents saved on their device.
• Searchable list & recent history: Keeps track of opened documents, enabling quick reopening and providing search and filter capabilities.
• Bookmarking/favorites: Track important PDFs via favorites, leveraging SharedPreferences for lightweight data persistence.

Although there’s no explicit code sample in the README, developers can review the repository to see how to initialize PDFium in Kotlin or Java:

val pdfRenderer = PdfiumCore(context)
val fd = ParcelFileDescriptor.open(file, ParcelFileDescriptor.MODE_READ_ONLY)
val pdfDocument = pdfRenderer.newDocument(fd)

This snippet highlights how the PDFium API is accessed in an Android environment.

Maintained by Mudlej since August 2022, the project has delivered multiple iterations—including nine official releases and active forks with updates like translation and icon changes. The source is published under the GNU General Public License v3.0 (GPL‑3.0), meaning you’re free to use, modify, and redistribute the code as long as any derivatives remain under the same license. This ensures copyleft protection: any enhancements must also be open‑sourced under GPL‑3.0.

This license is appropriate for developers seeking a robust PDF engine in their apps while complying with open‑source distribution obligations. However, if you plan to incorporate MJ PDF Reader’s code into proprietary apps without re‑licensing under GPL‑3.0, you should consult legal guidance.

Metadata

• Author: Mudlej
• Programming Language: Kotlin / Java (Android)
• License: GNU General Public License v3.0 (GPL‑3.0 or later)
• License Constraints: Copyleft applies—any derivative code must also be released under GPL‑3.0.
• Repository Link: https://gitlab.com/mudlej_android/mj_pdf_reader