The problem is not connected with the fact that the WebViewer does not support multiple columns. Have in mind that this is just a CTP release and there are many features still missing. We are planning to support multiple columns in a later version. The problem is that HTML is not page-oriented format, therefore we do not recommend printing directly from the web page. You still can do that if the results satisfy you. We simply suggested using the WinViewer for better results. The HTML rendering extension does not use physical pages with dimensions in the same way the image rendering extension does. It is designed primarily for viewing reports. Besides, we cannot rely on the web browser's print function and expect the same results across different browsers. Therefore, if the end goal is to get a printed page, I would suggest using the PDF or TIFF exports. You will be able to export to these formats from both the WinViewer and the WebViewer.
This is still just a CTP version and there are no wizards for creating different kinds of reports. We are planning to provide such wizards at a later stage. For now you can try to configure the report manually by setting PageSize, Margins, ColumnCount, and ColumnSpacing following the labels' specification