This viewer is a document viewer that uses tabs to view multiple documents at once.

From the site:

It uses Poppler for PDF support, libspectre for PS support, DjVuLibre for DjVu support, CUPS for printing support and the Qt toolkit for its interface.

Current features include: * Outline, properties and thumbnail panes * Scale, rotate and fit * Fullscreen and presentation views * Continuous and multiple-page layouts * Search for text * Configurable tool bars * Configurable keyboard shortcuts * Persistent per-file settings * SyncTeX support * Rudimentary annotation support (with Poppler version 0.20.1 or higher) * Rudimentary form support * Support for PostScript and DjVu documents