A PUB file is a Microsoft Publisher document file format. It is used to create several types of design layout documents such as newsletters, flyers, brochures, postcards, etc. PUB files can contain text, raster and vector images. Documents created with PUB files are mostly used in websites and marketing materials such as Emails. PUB files can be opened with Microsoft Publisher Desktop application, Microsoft Publisher 365, LibreOffice Draw, and Adobe InDesign.
PUB File Format - More Information
PUB files are stored as binary files do disc. Contents of a PUB files can also be converted to DOCX file format from within the Microsoft Publisher application by using the Save As option.
How to use Microsoft Publisher?
Microsoft has established several guidelines for helping users getting started with Microsoft Publisher. This Basic tasks in Publisher guide lets you get started by showing how to create a publication, saving a publication, adding text and building blocks, and printing publication.