The best open source alternative to SumatraPDF is Okular. If that doesn't suit you, our users have ranked more than 100 alternatives to SumatraPDF and many of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to SumatraPDF are Evince, MuPDF, KOReader and Librera Reader.
Multi-platform document viewer offering extensive format support, including PDF, comics, images, EPUB, and Markdown, with annotation tools, sidebar previews, text-to-speech, DRM management, cross-platform compatibility, and integration with KDE Frameworks libraries.
Evince (or GNOME Document Viewer) is a document viewer for multiple document formats: PDF, Postscript, djvu, tiff, dvi, XPS, SyncTex support with gedit, comics books (cbr,cbz,cb7 and cbt) and others. See Supported Document Formats for details.
MuPDF offers a highly versatile PDF, XPS, and eBook interpreter, customizable as a renderer, viewer, or toolkit. Features include digital signatures, redactions, form filling, annotations, and page manipulation, ideal for mobile, eBooks, and embedded apps supporting Java, C++, and Python.
An ebook reader application supporting PDF, DjVu, EPUB, FB2 and many more formats, running on Kindle, Kobo, PocketBook, Linux and Android devices.
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 an all-in-one e-book reader that can help you better manage and study your e-books. It's free and open-source.
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.
Openlib is an open source app to download and read books from shadow library (Anna’s Archive). The App Has Built In Reader to Read Books.
Sioyek is a PDF viewer with minimal interface optimized for reading research papers and technical books.
Discover uRead, your ultimate companion for reading and listening! Whether you’re a casual reader or a book enthusiast, uRead transforms your experience with advanced features and a user-friendly design.
A document viewer for the GNOME desktop. You can view, search or annotate documents in many different formats.
Germany
EU
United States
Slovakia
Because both programs are design to see documents.