If you already use any of the JetBrains IntelliJ IDEs (I wouldn't recommend installing them just for this purpose) then there is an AsciiDoc plugin available.
Open an AsciiDoc from File->Open menu, it will show the plain text.
Top right it should indicate a plugin is available, click on the link and install the plugin.
Bottom right it should suggest for you to restart the IDE to make the plugin active. Click "Restart" and wait for IDE to restart.
You will get a dual-pane view (text plus preview) of the doc, like this:
And at the top of this pane you have some controls, among them the ability to view just the raw text, both, or just the preview.