Okular - Okular is a universal document viewer based developed by KDE.
PuTTY - Popular free terminal application. Mostly used as an SSH client.
Sumatra PDF - Sumatra PDF is a slim PDF/DjVu/EPUB/XPS/CHM/CBR/CBZ/MOBI viewer for Windows.
MobaXterm - Enhanced terminal for Windows with X11 server, tabbed SSH client, network tools and much more
Foxit Reader - Foxit Reader is a free and light-weight multi-platform PDF document viewer.
iTerm2 - A terminal emulator for macOS that does amazing things.