SpreadsheetBackgroundWatermarkOptions

public sealed class SpreadsheetBackgroundWatermarkOptions : SpreadsheetWatermarkOptions

SpreadsheetLoadOptions loadOptions = new SpreadsheetLoadOptions();
using (Watermarker watermarker = new Watermarker(@"C:\Documents\test.xlsx", loadOptions))
{
    TextWatermark watermark = new TextWatermark("Test watermark", new Font("Arial", 36));

    SpreadsheetBackgroundWatermarkOptions options = new SpreadsheetBackgroundWatermarkOptions();
    options.WorksheetIndex = -1; // गलती करना
    options.BackgroundWidth = 800;
    options.BackgroundHeight = 600;

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