GroupDocs.Watermark API allows you to search the possible watermarks placed in any document. You can also search the watermarks that are added using some third-party tool. The found possible watermarks can be removed or their properties can be changed. For more details please refer to the following guides:
Searching watermarks Modifing found watermark properties Removing found watermarks...Classification Product Solution Purchase...
This section decsribes how to add digital signature to pdf, docx, pptx, xlsx and many more with GroupDocs.Signature for .NET library...Classification Product Solution Purchase...
Working with XMP metadata GroupDocs.Metadata for Java also allows managing XMP metadata in MP3 files. For more details please refer to the following guide: Working with XMP metadata...Classification Product Solution Purchase...