Found another issue when embedding the Report Viewer within a bootstrap site. I found all my reports showed what looked like cell spacing in a table - see TelerikReportingBootstrapBefore.png. This happened in Normal Viewing mode and Print Preview mode.
All you need to do to fix it is add the following bold text before the #reportViewer1 style. This fixes the issue for the report viewer and turns the report back to normal - see TelerikReportingBootstrapAfter.png.
<style>
* {
box-sizing: content-box!important;
}
#reportViewer1 {
position: absolute;
left: 5px;
right: 5px;
top: 5px;
bottom: 5px;
height: 100%;
overflow: hidden;
font-family: Verdana, Arial;
}
</style>