I have the same issue.. but do not see that your response answered the question. How does one export as a .pdf ?
In Photo Mechanic, you would go through the
File-->Page Setup and
File-->Print steps to either print a contact sheet or proofs, then use your operating system's option to print to PDF.
For newer Windows operating systems, there should be a "Microsoft Print to PDF" as a printer choice that will create a PDF.
For MacOS: at the bottom of the MacOS print settings window is a dropdown menu "PDF". Selecting that will reveal a "Save as PDF" option. Screenshot attached for reference.