How do I add text on a path (e.g. circle) to PDF?

Q: Do you have any suggestions on how to add text to a PDF to follow a
A: To draw text on a path you would need to create text run for each
character and then individually position each character with a
transformation matrix (that would also include the rotation component
besides advance width displacement).

There is good MSDN article by Charles Petzold 'Render Text On A Path
With WPF' that talks about this topic in detail and includes all
relevant source:

Since PDFNet support conversion from WPF/Xaml to PDF (and other
formats) you could potentially use the code without major
modifications. If you need to merge the content with the existing
approach you can copy the elements from the temporary page to the
target page as shown in ElementEdit or Imposition () samples.

Alternatively is you want to use ElementBuilder/ElementWriter to draw
text on a path without using WPF/Xaml you can use the same technique
that is described in the article.