When creating a new report, check Add Page Totals option at the last step of the wizard. All objects will be created automatically for each numeric field of data source. Then, in Report Builder you will be able to remove the objects for those columns, for which you don't want to show the page totals, as well as to add new such objects.
To modify an existing report, choose Report Builder page. Mark with check the Page Totals band in report tree to make it visible. Place Expression objects on it. Call the Expression editor (button '...' in object properties table). Select dataset_sum from the function list and click Add button to the right. In the editor, specify values for the second and third parameters of the function: -1 (group by current page) and the needed field name in single quotes, respectively. Then click OK. Repeat this procedure for all columns, for which you wish to add expressions.
Click Preview. In preview, click Print, select print options and click OK.
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