If you are using export to pdf for this, you should take a look at this documentation article
And for your specific case, you can register for the HTMLCellFormatting
event and do the following:
sender, Telerik.WinControls.UI.Export.HTML.HTMLCellFormattingEventArgs e)
var boolValue = (
e.HTMLCellElement.Value = boolValue ?
If you have any other questions, please let me know.