There are two known ways to convert an OST report into an Adobe PDF. The first is to do so using MS Outlook by manually exporting emails from your OST report to Adobe PDF files. You will first fire up Outlook, and then you will highlight the emails you wish to migrate. Then you will select "Print" in your Outlook and save it as a PDF file. Indeed, for those "small" amounts of data, this method makes life a lot easier.
The second method is the use of an OST to PDF Converter Software developed by WebbyAcad. Bulk conversion of the OST file into the PDF format is made easy with this software, thus making it perfect for those users who prefer a swifter and more reliable migration process at the same time. The software does not make any changes to the formatting or structure of the emails as the original format is retained. The software, with its easy user interface immediately gets bulk MAT, and strong features help it deliver uninterrupted conversions for all your OST to PDF requirements.

more details on:- https://www.webbyacad.net/blog/top-software-solutions-to-convert-ost-file-to-pdf-with-attachments/