"Such a tool appears to not exist - the search I did only came back with the following article:
Why Can't I View .PUB Files? It’s one of the great mysteries of the world – why don’t Microsoft provide a free viewer for Microsoft Publisher (.pub) files? As yet, it hasn’t been explained and there doesn’t seem to be anyone presenting a third party alternative. The result of this of course is that anyone wishing to view a Microsoft Publisher document must do so on a PC with the application installed on it, or else view a printed copy of the document! Read more: http://www.brighthub.com/computing/windows-platform/articles/52304.aspx#ixzz0V75pJTkg"
I find that Inkscape does a fairly good job at designing documents. As far as I know there is no program that allows for you to open PUB files on Linux.