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Orion Viewer vs MJ PDF: catalog facts
Orion Viewer	MJ PDF
Free Free and open source under the GPL.	Free Free and open source under the GPL 3.0 licence.
Android	Android
Opens DjVu as well as PDF, XPS, CBZ and TIFF Configurable tap zones and key bindings for page turning	Library view with recent files, folders and reading history Dark mode for the PDF content as well as the interface
Viewer only, with no PDF editing Interface is functional rather than polished	Android only A reader with annotations rather than a full PDF editor
Downloadable app	Downloadable app
Open source	Open source
License: GPL-3.0-or-later	License: GPL-3.0-only
No account needed	No account needed
Works offline	Not stated if it works offline
Official website Full listing and sources Checked October 2, 2026	Official website Full listing and sources Checked October 2, 2026

Catalog facts only. Anything “not stated” is unconfirmed. Check full listings for details.