It is very easy to convert OST files to PDF format. You need just reliable software that can easily convert multiple OST files at once, and allow you to convert the needed data instead of entire OST files. When I need to convert an OST file to PDF format, I use
ToolsGround OST to PDF Converter. It can easily convert an OST file to PDF format without any data loss. It supports all versions of Windows and MS Outlook, and doesn't work with Exchange Server and MS Outlook for the conversion process. It offers a trial version for all users, so they can easily understand it.