Thanks for using GroupDocs.Viewer and sharing your issue with us. We are able to reproduce the issue of missing character ‘t’ at our end. The issue has been logged in our Issue Tracking System (with ID: VIEWERNET-1506) for further investigation by the product team.
However, we could not reproduce the issue of header/footer (see output). The header is also fine in the application that you have shared with us. Furthermore, the screenshot you have shared with us shows that you are using one of our open source document viewer applications. If yes, would you please mention its name? We shall be looking forward to your response.