Hi Bala,
Thank you for reaching out to Syncfusion support.
We have thoroughly reviewed the reported issue on our end. After detailed analysis, we were unable to reproduce the problem. In our testing, the Table of Contents (TOC) content in the output PDF document does not contain any boxes, and the reported behavior could not be replicated. Please refer to the screenshot below for confirmation:
Screenshot:

For your convenience, we have attached a sample project along with the corresponding output PDF document.
Please try running the provided sample on your end and let us know the results. If you continue to experience the issue, we kindly request you to share the following details with us:
- A reproducible sample or complete code snippet
- Syncfusion package name and version
- .NET version
- Environment details
This information will help us analyze the problem more effectively and provide you with a prompt solution.
Regards,
Arumugam M
Attachment:
HTML_to_PDF_NET_a5708c7b.zip