Pfx certificate file and Microsoft Store
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If you bundle your applications as a MSIX file, Microsoft will sign them for you after you submit them to the store. If you want to publish a traditional installer, you need to sign it yourself.
PFX certificates are no longer issued for code signing by trusted CAs, only cloud signing or HSM is allowed (when you buy a new certificate, you can get a small security token shipped to you that holds the private key for the certificate). I don't know what your idea of "low price" is, but $300-$500 is about what those things cost. There are CAs that subsidize most of the cost for Open Source projects.