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Are any of these answers pertaining to an mbox file residing in the Finder?

Yep.

Screenshot 2024-12-01 at 20.51.23.png
 
I was thinking the OP wanted to print directly from an MBOX file and not going through an Mail app import process etc.
I agree. But really importing to Apple Mail and Export to Pdf is so easy and free. The process using another (probably paid) app would be similar.
 
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