Apache OpenOffice - Apache OpenOffice is an open source, office document productivity suite.
Foxit Reader - Foxit Reader is a free and light-weight multi-platform PDF document viewer.
LibreOffice - Free office suite, open source, and compatible with .doc, .docx, .xls, .xlsx, .ppt, .pptx files. Updated regularly – download for free. Originally based on OpenOffice.org.
DjVuLibre - DjVuLibre: Open Source DjVu library and viewer
Microsoft 365 - Boost your productivity with reliable access anywhere with services like email, calendar, file sharing, meetings, instant messaging, and Office Online
Sumatra PDF - Sumatra PDF is a slim PDF/DjVu/EPUB/XPS/CHM/CBR/CBZ/MOBI viewer for Windows.