It is free.

[Main menu>Tools>Settings…>Watermark]

If you would like to watermark pictures use this option. Select “Use selected watermark” and select small picture as watermark (we recommend “*.png” format watermarks, how ever you can use other formats). Also you can select watermark position on your image.
If you do not have your own watermark we would be glad if you support us and put at least “vxei-small.png” watermark which you can find under vxei picture uplader installation path “watermarks” directory.