C# .NET API to add, search and remove image & text-based watermarks from documents: PDF, Word, Excel, presentations, Visio, email and image file formats....Microsoft Word, Excel, PowerPoint, Visio, OpenDocument, JPEG, BMP, PNG...PPSX, PPSM, PPTM, POTX, POTM Visio: VSD, VSDX, VSDM, VSTX, VSTM...