Any drawing or chart created in Microsoft Visio, but saved in XML format has a VDX extension. A Visio drawing XML file is created in Visio software, which is developed by Microsoft. Microsoft Visio has the capability to generate visual documents that can be used in presentations and documents. The Visio drawing XML file contains the visual objects and metadata details of the visual elements.
You can also add watermark to many other file formats. Please see the complete list below.