winget
If you already use winget:
If you do not have it yet, see how to install winget.
winget install StirlingTools.StirlingPDF
Scoop
Official docs also list Scoop. Commands below match that page. If Scoop packaging changes, trust the official Windows installation docs.
scoop bucket add stirling-pdf https://github.com/Stirling-Tools/homebrew-stirling-pdf scoop install stirling-pdf/stirling-pdf