C# .NET API To add, search and remove image & text-based watermarks from documents: PDF, Word, Excel, presentations, Visio, Email and image file formats....DOCM, DOT, DOTX, DOTM, RTF, TXT Excel: XLS, XLSX, XLSM, XLSB...Format : PDF Open Document : ODT Email : EML, MSG, EMLX, OFT Images...