For a very long time I have been using the litte freeware app EncryptOnClick (EOC),
to be downloaded from here (the same makers as SyncBackFree).
After installation, the app adds a context menu (right click) action. by which you can encrypt a file. It will do exactly the same as when you zip a file while encoding it but easier. It will replace the normal file by the encoded file, while safely erasing the original file. The extension will be changed into EOC.
If you click any file that ends with EOC, the app will be started and you get a window asking the password. Fill in the correct password and the file will be decrypted again. If you don't have the app installed anymore on the system, files can be decrypted by changing the extension into .zip and using a regular unzip app.
So it's just the ease of using encryption and decryption that is making the app worthwhile.
I stopped using the app for one simple reason only. Because I am rather old and I were the only one in the family using this app, I feared that important files, that have been encrypted in this way, could not be opened by my wife or my son in case I would not be able to do it anymore. So I decided to only encrypt pdf's (which you get an automatic question for opening password when doubleclicked). And transfer all important files that are connected with banking and other delicate stuff into readable pdf's (like emails, simply printing them to encrypted pdf's).
That I have been doing now for several years, but the app EOC still exists in updated form and certainly will do what it did, when I was still using it.