var docRef = app.activeDocument;

var sampleText = docRef.textFrames[0];
// var numberOfFonts = app.textFonts.length; // all the fonts; alternative on line 5
var numberOfFonts = 30;

var spacing = 20;
var greatestWidth = 0;
var startX = 0;
var startY = 792;

var xPos = startX;
var yPos = startY;

for (var i = 0; i < numberOfFonts; i++) {
	var myText = docRef.textFrames.add();

	myText.textRange.characterAttributes.textFont = app.textFonts[i];
	myText.textRange.characterAttributes.size = 18;
	myText.contents = sampleText.contents;
	
	myText.top = yPos;
	myText.left = xPos;
	
	if (myText.width > greatestWidth) {
		greatestWidth = myText.width;
	}
	
	if ((yPos - myText.height - spacing) <= 0) {
		xPos += greatestWidth + spacing;
		yPos = startY;
		greatestWidth = 0;
	} else {
		yPos -= myText.height + spacing;
	}
}