Someone sent me a MS Publisher file. That is a problem, even if you are on a Windows box. You need to have the correct version of Publisher installed, because there is no reliable compatibility between different versions. A classic M$ trick, I dare say. And besides, I am locked in to a Linux box, of course.
One can search the web down to its very foundations, but there simply is no way to open a PUB file outwith Publisher. Another typical Microsoft feature. Then what to do? I found two options.
LibreOffice does have a converter included, since version 3.7. A dedicated work of reverse engineering it is. The library – libmspub – mainly covers the MS Office 2002 format, with support for earlier versions, and most likely offers some coverage for MS Office 2013 too. However, in my case it did not work well at all. The PUB file was basically useless once opened in LibreOffice.
Next option was the online service of Zamzar. It is free as in free beer. Upload your PUB file, select the desired format, give an email address, and soon you will find the converted file in your inbox. The conversion to ODT did not produce anything useful, as could be expected, but the PDF turned out a really neat document. There are more online services similar to Zamzar.
So, obviously this is as far as one can get in handling PUB files outwith MS Publisher, I guess: convert the file to PDF. Might you want to edit it, you probably have one easy option left: export the PDF file to plain text. Unless you are willing to pay for professional PDF editing software. Exporting to plain text will of course dump all lay-out, links, charts, images etc. Okular can do this export straightforwardly.