First of all thank you for the positive feedback.
Unfortunately we don't support exporting images in wmf format. The reason for this is that Silverlight does not support wmf as an image format, so when a document is imported from rtf, all wmf (and also bmp) images are converted to png in order to be displayed correctly. The result is that all wmf data is lost during the import process and cannot be exported.
We'll be glad to help you further if you have more questions.
All the best,
the Telerik team
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