It is unlikely that you will find some kind of utility or converter designed for direct pdf to cbr conversion, which is something like a creation of ComicBook archive (.cbr) from a PDF document. Nevertheless you can still do it manually should you really need it.
The key will be in producing a picture from your PDF document, so each page is saved as a single JPEG picture. Once this is done, rename all files to a numbered sequence (001, 002, 003 etc.) and compress it as RAR archive. The last step will be just to rename the suffix from rar to cbr and that's it.Open PDF file Open CBR file