Files with .VSDX extension represents Microsoft Visio file format introduced from Microsoft Office 2013 onwards. It was developed to replace the binary file format, .VSD, which is supported by earlier versions of Microsoft Visio. It is also supported on Visio Services in Microsoft SharePoint Server 2013 and does not require an intermediary file format for publishing to SharePoint Server.
You can also add watermark to many other file formats. Please see the complete list below.