Hello Santosh Kumar,
The problem is that the HTML that Internet Explorer puts in the clipboard is mostly script, which cannot be used to create a RadDocument. You can try adding a reference to Telerik.Windows.Documents.FormatProviders.Rtf. In this way, the content of the clipboard which is in RTF format will be used when pasting. The only limitation we are aware of is that the images would not be pasted, as they are added in the RTF as IncludePicture field, which is not supported.
We will adjust the pasting for the next official release, so that if the HTML and RTF that are in the clipboard create an empty document, the paste will fallback to plain text.
the Telerik team
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