Files with VSTX extensions are drawing template files created with Microsoft Visio 2013 and above. These VSTX files provide a starting point for creating Visio drawings, saved as VSDX files, with default layout and settings. In general, Visio files are used to create drawings that contain visual objects, flow charts, UML diagrams, information flow, organizational charts, software diagrams, network layout, database models, objects mapping, and other similar information.
You can also add watermark to many other file formats. Please see the complete list below.