If you use Microsoft Publisher, you might be interested to know that Publisher is not available for Apple users. Anyone using an iMac or MacBook is free to buy and install Microsoft 365, like anyone else. But after the install, the Apple computer will offer Word, Excel, PowerPoint, etc., but NO Publisher.
It’s not such a big deal, until someone sends a Publisher file to a Mac user. Then the trouble starts: the Mac will be unable to open or show the file, and it will offer no help as to what to do!
Since there is no way to get Publisher for MacOS, here are some workarounds:
LibreOffice can open Publisher files, as well as allow for some editing. Install it for free from their website.
Convert the File to PDF
There are plenty of free websites that can convert an unopenable file to a PDF version. The converted file will then easily open in Adobe Reader or your browser. Consider uploading the .pub file to PublisherToPDF.com for this option.
Ask the File Creator for a Different Format
You can always let the sender know that you don’t have access to Publisher. They may be able to save their work as a PDF and send that over to you, instead!