Hi,
Thank you for your interest in Syncfusion Products.
Regarding your query about copying a block between two bookmarks and adding the same at the end of the third bookmark, we have prepared the sample to illustrate the same. The sample is available in the below link. Try running the sample and let us know if it was helpful.
Sample:
http://www.syncfusion.com/downloads/Support/DirectTrac/88684/BookmarkSample1030517846.zipPlease let us know if you have any questions.
Regards,
Lakshmi Devi S