I have asked Pubit support the same question and have not received a reply.
The only field I see in the Pubit info form is the one that asks if you have a print version and asks for the number of pages of the printed version.
Does anyone know how B&N links the nook version to the printed version?
They answered me via email. They told me to make sure that my author name and book name for my printed version and ebook version match identically. Also, if you used a middle inital in one, then use it in the other as well. If things are identical then they will be matched in the system in a few days. It worked for me