Why in the world are you creating such a large document/file in Publisher? It would seem to be more efficient in other software (Visio, PowerPoint, AutoCAD, et al).

FWIW, I tried to set up a page in Publisher measuring 72" x 72". Each time it reverted back to what appears to be Publishers maximum of 17" x 36" (or, something like that...I did not pay close attention). So, apparently, Publisher has its limitations.