This code example demonstrates how to implement setting custom margins in the ASPxSpreadSheet.
To test the functionality, choose menu item Margins - Custom Margins, set preferable values and open a document preview using File - Print menu.
UPDATED:
Starting with v15.2, the new Page Setup dialog was introduced, providing a set of print-related options (document orientation, paper size, page order, etc.) and making it possible to set custom page margins (Specify Print Options). See this in action in our Spreadsheet - Printing online demo.