Open Source Apps with 'PDF annotation' feature

Open-source browser with Gecko engine, supporting HTML add-ons and providing privacy features like Enhanced Tracking Protection and third-party cookie blocking.

Free open-source suite with advanced photo retouching, composition, batch processing, plugin extensibility, custom scripting, and wide file format compatibility.

A free, open-source viewer for Windows, supports PDFs, eBooks, Comics, with a simple, fast, and portable design prioritized for ease of use.

Open-source suite for editing documents, spreadsheets, presentations, forms, and PDF files with co-editing modes, plugin support, AI assistant, and integration across 40+ platforms.

Local-first, privacy-focused notebook supporting Markdown and Org mode, offline use, encrypted backup, extensible with plugins, and more.

Multi-platform document viewer supporting PDF, EPUB, comics and images with annotation tools, sidebar navigation, signature verification, and text-to-speech.

Zotero is a free, easy-to-use tool to help you collect, organize, share research and cite your research sources directly in your favourite word processor, with 300 MB free online storage.

Handwritten notes and PDF annotation app with pen input, shape drawing, customizable toolbar, image insertion, audio recording, and multi-platform support.

Displays PDF, Postscript, DjVu, comic books, TIFF, DVI, XPS formats, supports editing PDF annotations, remembers individual zoom and position settings, includes search.

locally hosted web application that allows you to perform various operations on PDF files.

An ebook reader application supporting PDF, DjVu, EPUB, FB2 and many more formats, running on Kindle, Kobo, PocketBook, Linux and Android devices.

Highly versatile PDF and XPS solution offering customizable rendering and viewing with features like digital signatures, redactions, and annotations.

Librera Reader is a highly customizable and feature-rich application for reading books in PDF, EPUB, MOBI, DjVu, FB2, TXT, RTF, AZW, AZW3, HTML, CBZ, CBR formats on Android devices.

Koodo Reader is a powerful ebook reader designed to provide a simple and easy-to-use reading experience.

Free and open source desktop application to split, merge, extract pages, rotate and mix PDF files.

A simple and modern eBook viewer for Linux desktops.

BentoPDF is a PDF Toolkit that works fully offline with no sign ups. It's fast, secure and forever free. In an era where data is a commodity, we take a different approach. All processing for BentoPDF tools happens locally in your browser.

Butterfly is a note-taking app where your ideas come first. You can paint, add texts, and export them easily on every device. This app works on android, windows, linux, and in the web.

HelixNotes is a local markdown note-taking app built with Rust, Tauri 2.0, and SvelteKit. Your notes are standard .md files on your filesystem - sync with whatever you want or nothing at all.

PDF Viewer (aka pdf.js) is a new revolutionary extension using web standard technologies that allows you to display within Mozilla Firefox almost all PDF files found on the web without a plugin.

Rnote aims to be a simple but functional note taking application for freehand drawing or annotating pictures or documents. It eventually should be able to import / export various media file formats.

Qiqqa is a free research and reference manager. Search for, read and annotate your PDFs. Then review your work, write up and create bibliographies instantly.

EmbedPDF is a framework-agnostic, MIT-licensed PDF viewer that drops into any JavaScript project. Whether you build with React, Vue, Svelte, Preact, or vanilla JS, EmbedPDF delivers a smooth, modern reading experience and a clean developer API.

Episteme Reader is an offline-first application designed for reading various document formats. It leverages native Android technologies and C++ libraries to provide a performant reading experience with customization capabilities.

Open-source tool for macOS with region, window, and fullscreen capture modes, local OCR, fast annotation, customizable backgrounds, and menu bar access.