KDE's universal document viewer: reads PDF (via Poppler), EPUB, DjVU, Markdown, images, and CBR/CBZ comic archives through a shared plugin architecture, so the same viewer UI works across formats. Adds inline and popup annotations, highlights, underlines, and freehand text; views and verifies embedded digital signatures and can sign PDFs itself; offers text selection with a magnifier tool; and provides thumbnail navigation alongside an auto-generated table of contents.
Licensed GPLv2+.