Turn on Options|Visualize Spaces if you want spaces and tabs to be visualized. Spaces will be indicated by a vertically centered dot. Tabs are indicated by a » character. This option is useful when working with files where extraneous whitespace can lead to problems, or where the difference between tabs and spaces matters.
You can set the color of visualized spaces in the Colors Preferences. If you set a background color other than "default" for whitespace in the preferences, then spaces will always be drawn with that background color, whether you've turned on the option to visualize them or not. Spaces will then appear as colored rectangles, with or without the symbol.
Note that "visualize spaces" is a file type specific setting in EditPad Pro. If you change the setting through the Options menu or the toolbar, it is applied to the active file only. If you create a new file or open an existing one, the setting made in File Type Editor Options for the type of file you are creating or opening, will be used. Also, when you use File|Save As, and you save the file with a new extension, then the setting for the current file will change into what you specified in File Types Preferences for the file type that corresponds with the file's new extension.
Convert|Tabs -> Spaces
Convert|Spaces -> Tabs
Convert|Indentation Spaces -> Tabs