Files with .VSX extension refer to stencils that consist of drawings and shapes that are used for creating diagrams in Microsoft Visio. VSX files are saved in XML file format and was supported till Visio 2013. These are different than the primary VSDX file format that was introduced with Microsoft Visio 2013. VSX files can be opened in any text editor to view the contents.
You can also add watermark to many other file formats. Please see the complete list below.