The printing settings RadSpreadsheet exposes control the way the visual which is sent to the printer will look. For example, if you set the page size to A3, the range of cells included in this visual will be larger. In Silverlight, there's no way to access the actual printer settings due to security limitations of the framework and indeed, the settings of the PrintDialog take precedence. In other words, to print to A3 paper (or with Landscape orientation), you need to specify this both for RadSpreadsheet in the print preview control and for the printer in the PrintDialog.
As to your question on modifying the preview control, you can extract and change the style of the PrintPreviewControl and remove any options you don't want to be visible. The attached application demonstrates how this can be achieved - it uses the Windows8 theme and our implicit theming mechanism.
I hope this helps.
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