Okular - Okular is a universal document viewer based developed by KDE.
Exstora - Built-in quick note: save ideas, contacts, interesting facts
Sumatra PDF - Sumatra PDF is a slim PDF/DjVu/EPUB/XPS/CHM/CBR/CBZ/MOBI viewer for Windows.
TINYpulse Engage - Increase Your Employee Engagement. Instantly.
Foxit Reader - Foxit Reader is a free and light-weight multi-platform PDF document viewer.
OneNote Online - OneNote Online, part of Office Online, is the online version of Microsoft OneNote.