I would like to use GroupDocs.Viewer-for-.NET-UI as codebase and reivse it for our customer need. How to dynamic add image watermark(not text watermark) to each view page(png view) when rendering?...I would like to use GroupDocs.Viewer-for-.NET-UI as codebase and reivse it for our customer need. How to dynamic add image watermark(not text watermark) to each view page(png view) when rendering?