This is indirect access to this service. Please refer to the corresponding SDK below. GroupDocs.Watermark is a .NET API to digitally add text and image watermarks on most common and popular document formats including Microsoft Office (Word, Excel, PowerPoint, Visio), OpenDocument, PDF, Email and images. The smart searching feature is very useful in terms of locating hard-to-find watermarks and remove them from documents. With GroupDocs.Watermark library – secure your sensitive documents from unauthorized access.