Draw Spaces
The Draw Spaces plugin is a simple plugin that can mark spaces, tabs, and other types of whitespace with a small, visible marker. By making whitespace visible, you can more easily see how whitespace is used in a document, and can apply spacing strategies more consistently.
To enable the plugin:
Press the menu button in the top-right corner of the window and select Preferences ▸ Plugins.
Select Draw Spaces to enable the plugin.
Press Preferences to set its options.
Though you will be able to see the markers when you work on a file, the markers will not be visible when you print a file to paper.