The interactive layout removes the strict restrictions for report pagination on the client by utilizing a simpler paging algorithm, which allows it to render reports faster. For example, if you use the crosstab's drill-down feature, the crosstab will expand its subcategories faster, because it will not recalculate the report's page size. The new mechanism is based on soft page breaks, where the report is optimized for screen-based viewing and delivery. In other words, you could have a two-page long table which to appear in a single continuous form on the client with a vertical scroll bar (logical layout); when printed, the table will print on two separate sheets of paper (print layout).
In this line of thoughts in interactive mode one data item such as table will be rendered on a single page
In the Print Preview layout the pages will be calculated based on the page settings and the report will be centered. However the Print Preview will not be interactive, because it is dedicated for printing preview only.
If you prefer the Print Preview view mode you can make it default is elaborated in Disabling new feature "Interactive view " by default forum thread. The forum thread elaborates on the WPF report viewer, but you can utilize the same approach for the Silverlight report viewer.
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