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The illustration of a PDF-file, in that transparent polygons were received, is really slow or the transparence of color is lost on paper or in a PDF-document.
The reason is due to program libraries, GDI+ and the Postscript drivers, that do not work together correctly and that we are not able to change. Workaround:
Generate a SVG file 'optimized for Inkscape' in Visum. Then, convert this file to PDF in Inkscape via File -> Save as -> PDF via Cairo.