This is a legacy report viewer and for new projects our recommendation is to use the latest web forms report viewer - HTML5 Web Forms Report Viewer
This article elaborates on the specifics for printing a report on the client side.
The True printing is the only way to support multi-page reports printing in most of the browsers. The True print is rendering the report in PDF with special settings so when the PDF file opens in browser, the PDF plug-in print dialog is invoked. This functionality is available for the ASP.NET report viewer and Silverlight report viewer.
If you want to use the True print, the following requirements must be satisfied:
Disable any other PDF related plug-ins such as Foxit.
UnmanagedCode permission is required due to the used PDF rendering. See Medium Trust Support
(Silverlight viewer only) UseNativePrinting property should be false. Telerik Reporting WCF Service should be properly configured e.g. resource endpoint should be present.
(Internet Explorer only) Print menu
(Internet Explorer only) ActiveX Filtering should be disabled.
The Silverlight report viewer additionally supports Silverlight Native print so you can avoid the True print requirements. In order to enable the Silverlight native print set the UseNativePrinting property to True.
In Firefox 19+ the default viewing option for PDF files is the PDF.js, which is not added as a plug-in and Firefox does not expose the content type viewing preferences - Firefox bugs. Thus the Adobe PDF plug-in is always active whether or not it is the preferred viewing option. To ensure the print operation in Firefox will be accomplished, clicking the print button would export the report to PDF which will be printed with the available client viewing tools.