A file that cannot be opened on a MAC is a file with the extension “.pub” created by Microsoft Publisher.
If you are using Windows, you can use this Publisher to do layouts, etc., but it cannot be opened on Mac, and it is quite a problem if you receive a “.pub” file.
I found a website that allows you to convert such “.pub” files to PDF.
That is this site called ONLINE 2 PDF.COM!
Usage is simple.
Press the “Select files” button at the bottom center of the screen, select and upload the Publisher (.pub) file you want to convert to PDF.
Click the “Convert” button below.
It will take some time, but it will convert to PDF.
Conversion accuracy is also quite high.
This is a highly recommended site as it allows you to view Publisher files even on a MAC!