Thank you for the details. Please note, you are using an old XML structure in your input templates and the latest version 17.6 of Aspose.Pdf for .NET API does not support it. You can use only the old versions of Aspose.Pdf for .NET API to manipulate the old structured XML templates and we do not provide fixes in the old code base.
We would recommend you to convert the old XML templates based on the new XML structure, and then convert XML templates to the PDF format. We have created an XML template with HTML bold tagtemplatenew.zip (396 Bytes), and it works fine in the new DOM approach Resultant_17.3.pdf (53.8 KB).
// instantiate Document object
Document doc = new Document();
// bind source XML file
// save resultant PDF file
Please let us know in case of any further assistance or questions. In order to get more understanding, please refer to these help topics: Convert XML file to PDF and Add HtmlFragment element in XML file. The ticket ID PDFJAVA-36867 has been closed.