If you implement the viewer yourself, there is an SDK call on disabling the print button.
If you just use InfoView as-is and do not want to touch the code, there is a Consulting Solution called BOInterface that Business Objects Global Services sells and that helps you to achieve what you describe very easily.
CR4E has a web DHTML viewer, for which you’d remove the print button via method call CrystalReportViewer.setHasPrintButton(false), and a desktop Swing viewer, for which you’d remove the print button via method call ReportViewerBean.setHasPrintButton(false).