A .pub file is a document created by Microsoft Publisher, a desktop publishing program used to create professional documents and marketing materials such as newsletters, flyers, brochures, postcards, etc. . The PUB file extension is used to represent the Microsoft Publisher document file format, which is widely used for different types of publications. PUB files are capable of containing text, raster and vector images. They are stored as binary files on disk.

To open a .pub file, you can use Microsoft Publisher itself by selecting File → Open from the programs menu bar, and then navigate to and open your PUB file. Other desktop publishing applications that can open PUB files include LibreOffice Draw and CorelDRAW. You can also convert PUB files to several file types, including PDF, JPEG, PNG, and more, using Microsoft Publisher. Some online converters like Zamzar also allow you to convert PUB files to other formats for free.