Some earlier versions of Adobe PageMaker seems to have once used or could import .pub files (publications) and process them for making new PageMaker documents (.pm7 for example). That seems to be only pub to pm7 conversion we know of atm.
Convert Publication document file to Adobe PageMaker 7 document.
We found 2 software records in the database related to .pub to .pm7 file format conversion.
Microsoft Windows software - convert pub to pm7 on Windows
One of the first desktop publishing programs on market
Convert from pub file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned pub to pm7. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Apple macOS / Mac OS X software - convert pub to pm7 on OS X
Mac version of once popular publishing program