// Double line spacing
    guiText.lineSpacing = 2.0;

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Example() {
        guiText.lineSpacing = 2.0F;
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Example():
        guiText.lineSpacing = 2.0F