Files with VSTM extension are template files created with Microsoft Visio that support macros. Unlike VSDX files, files created from VSTM templates can run macros that are developed in Visual Basic for Applications (VBA) code. A template file can be created in order to provide basic settings of the document that can be utilized to generate further documents with these settings.
You can also add watermark to many other file formats. Please see the complete list below.