Microsoft Publisher allows users export of its own documents (.pub files) directly to PDF document format (.pdf). This is the most convenient way how to perform pub to pdf conversion, but not everyone may have access to the program. It is likely that you can find and use other tools, such as LibreOffice with PubOOo extension, that will give you the option to Publisher files and export them to Adobe PDF.
Open PUB file Open PDF fileOn-line converting service that allows users to convert PUB files to PDF documents