You are not linking to a function with the prototype void Draw_Fonts(float).
If it's from a library you are not linking to that library.
If it's a custom function, you are not linking all the source files ( or you haven't define it )
Just post the line that gives you the error, or the lines that eventually caused the error to show up.
A short Google search told me that you might be doing some Direct3D related coding, and that you need to link d3d9.lib in order to make some functions visible. But that's really a shot in a *deep* dark.