Thank you for considering Aspose.Words.
Please note that it is not guaranteed that the output PDF document will look exactly the same as the input HTML. This is because Aspose.Words was originally designed to work with Microsoft Word documents and HTML documents are quite different.
Aspose.Words’ HTML engine tries to mimic the way the Microsoft Word works. To you, this means that if you convert HTML file into a Microsoft Word document or PDF using Aspose.Words, the output will appear almost exactly as if it was done by Microsoft Word. Moreover, I have attached two DOCX documents (one generated by Aspose.Words 13.2.0 and the other generated by Microsoft Word 2013) here for your reference. The first heading section appears to be the same in both output documents.
If we can help you with anything else, please feel free to ask.