using Spire.Presentation;
namespace DeleteTextWatermark_PPT
{
    class Program
    {
        static void Main(string[] args)
        {
            //实例化Presentation类，加载有水印的PowerPoint文档
            Presentation ppt = new Presentation();
            ppt.LoadFromFile("TextWatermark.pptx");
            //遍历每一张幻灯片， 查找水印文字内容所在的形状并删除
            for (int i = 0; i < ppt.Slides.Count; i++)
            {
                for (int j = 0; j < ppt.Slides[i].Shapes.Count; j++)
                {
                    if (ppt.Slides[i].Shapes[j] is IAutoShape)
                    {
                        IAutoShape shape = ppt.Slides[i].Shapes[j] as IAutoShape;
                        if (shape.TextFrame.Text.Contains("内部资料"))
                        {
                            ppt.Slides[i].Shapes.Remove(shape);
                        }
                    }
                }
            }
            //保存并打开文档
            ppt.SaveToFile("RemoveTextWatermak.pptx", FileFormat.Pptx2010);
            System.Diagnostics.Process.Start("RemoveTextWatermak.pptx");
        }
    }
}

using Spire.Presentation;
using Spire.Presentation.Drawing;
namespace DeleteImageWatermark_PPT
{
    class Program
    {
        static void Main(string[] args)
        {
            //实例化Presentation类，加载有图片水印的PowerPoint文档
            Presentation ppt = new Presentation();
            ppt.LoadFromFile("ImageWatermark.pptx");
            //遍历每一张幻灯片， 设置背景填充类型为None
            for (int i = 0; i < ppt.Slides.Count; i++)
            {
                ppt.Slides[0].SlideBackground.Fill.FillType = FillFormatType.None;
            }
            //保存结果文档到本地并打开
            ppt.SaveToFile("RemovePicWatermak.pptx", FileFormat.Pptx2010);
            System.Diagnostics.Process.Start("RemovePicWatermak.pptx");
        }
    }
}