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Secure PDF Viewer vs Orion Viewer: catalog facts
Secure PDF Viewer	Orion Viewer
Free Free and open source under the MIT and Apache-2.0 licenses.	Free Free and open source under the GPL.
Android	Android
Requires no app permissions Uses a sandboxed WebView to display PDF streams	Opens DjVu as well as PDF, XPS, CBZ and TIFF Configurable tap zones and key bindings for page turning
Android only	Viewer only, with no PDF editing Interface is functional rather than polished
Downloadable app	Downloadable app
Open source	Open source
License: MIT AND Apache-2.0	License: GPL-3.0-or-later
Not stated if an account is needed	No account needed
Not stated if it works offline	Works offline
Official website Full listing and sources Checked October 8, 2026	Official website Full listing and sources Checked October 2, 2026

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