Hi Mahesh,
Thank you for your query.
The issue you're encountering is due to the nature of how the underline is represented in the PDF. In this case, the underline is part of a graphic shape and not a text property (like font style or decoration). Because of this, Syncfusion's PDF library (Syncfusion.Pdf.AspNet 22.1.34) cannot detect it as underlined text.
Currently, it is not possible to detect underlined text from an existing PDF document when the underline is rendered as a separate graphical element rather than being embedded as a text style.
Regards,
Irfana J.