The only direct way how to convert VDX drawings as DXF drawings would be to use Microsoft Visio, because it supports the export to DXF by default. There is a trial version available on Microsoft website, so you can use that if you just need a few conversions done.
Convert Microsoft Visio drawing XML file to AutoCAD DXF Drawing Exchange Format.
We found 3 software records in the database related to .vdx to .dxf file format conversion.
Microsoft Windows software - convert vdx to dxf on Windows
A vector based diagramming software from Microsoft
Convert from vdx file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned vdx to dxf. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Visual processor used to create high quality presentations, charts and graphs
Multiplatform software - convert vdx to dxf on any platform
A vector graphics editor