In case that you looking for a way to convert MS Office files to PDF, check individual conversion entries based on the file types used in the programs, i.e. Excel (.xls, .xlsx), Word (.doc, .docx) etc.
Otherwise, the main type of mso to pdf conversion seems to be a situation when a user tries to convert Microsoft Organization Chart (.mso) as PDF. This cannot be done directly, however you can import organization chart to an MS Office document and save the result as PDF.
It is also known that some .mso files can also be found as e-mail attachment when the sender of the e-mail used MS Word or other programs as default text editor for MS Outlook. These .mso files cannot be converted to anything and they cannot be opened at all whatsoever. These .mso files are only visible because the receiver of the message does not use Microsoft Outlook and contain special formatting for the actual message. This is used so the recipient sees the document / message exactly the same as the sender.Open MSO file Open PDF file
A popular spreadsheet application distributed with Microsoft Office suite
A presentation program from the Microsoft Office suite
One of the most popular word processor program from Microsoft Office suite