7-Zip

7-Zip is a free, open-source file archiver that opens almost everything and compresses tighter than most paid rivals. A plain interface is the only real cost.

CCleaner

CCleaner is a PC cleaner for junk files, browser traces, and uninstall leftovers on Windows, Mac, Android, and iOS. The free tier still does the real work.

Sumatra PDF

Sumatra PDF is a free, no-frills PDF reader that opens files on Windows almost instantly, without Adobe’s bloat. See who it actually fits.

LibreOffice

LibreOffice is a completely free, open source Office & Productivity suite covering six apps, though heavily formatted Word and Excel files don’t always translate perfectly.