MuPDF viewer

Lightweight document viewerAGPL-3.0-or-later

MuPDF mini

Minimalist viewer for PDF, XPS, CBZ, unprotected EPUB, and FB2 documentsAGPL-3.0-or-later

APV PDF Viewer

PDF viewerGPL-3.0-only

Orion Viewer - Pdf & Djvu

Orion Viewer is pdf, djvu, xps, cbz and tiff file viewerGPL-3.0-or-later

Document Viewer Font Pack

Extra fonts for Document ViewerGPL-3.0-only

Librera Reader

Book and PDF readerGPL-3.0-or-later