SpreadsheetWatermarkShapeOptions

public sealed class SpreadsheetWatermarkShapeOptions : SpreadsheetWatermarkBaseOptions

SpreadsheetLoadOptions loadOptions = new SpreadsheetLoadOptions();
using (Watermarker watermarker = new Watermarker(@"C:\Documents\test.xls", loadOptions))
{
    TextWatermark watermark = new TextWatermark("Test watermark", new Font("Arial", 36, FontStyle.Bold | FontStyle.Italic));
    watermark.HorizontalAlignment = HorizontalAlignment.Center;
    watermark.VerticalAlignment = VerticalAlignment.Center;

    SpreadsheetWatermarkShapeOptions options = new SpreadsheetWatermarkShapeOptions();
    options.WorksheetIndex = 0;

    watermarker.Add(watermark, options);
    watermarker.Save();
}