How to retrieve the water mark .

this.addWatermarkFromText({
cText: "Hello" ,
cFont: "AngsanaUPC" ,
aColor: ["RGB", 1, 0, 0] ,
nTextAlign: app.constants.align.center,
nHorizAlign: app.constants.align.center,
nVertAlign: app.constants.align.top,
nHorizValue: -50,
nVertValue: -72 ,
nOpacity: 0.1 ,
});

}

from code above i add text "Hello" as the watermark . I have seen in javascript API reference that addWatermarkFromText(); will places the watermark in an optional content group (OCG).

my question is how can i get the text "Hello" back from watermark in document.