One of the possible jpg to pxd conversion we know of, would be making of Pixlr images (.pxd) from JPEG picture. As far as we know, this can only be with the Pixlr tool and no other. But since more than one file type use pxd extension, there might be perhaps another ways how to convert jpg to pxd to a different format.
Open JPG file Open PXD fileAn on-line photo editor