You can convert MBOX contacts to PDF by two different methods (1) Manual Method and (2) Professional method. But, I don't recommend you to use the manual method because the manual method is not the best practice to convert OST files and the manual method has its drawback.

- Manual method is a time taken process.

- Manual Method doesn't take responsibility for your data.

- In the manual method, you can't convert the MBOX file at the same time. 

Many other limitations of the MBOX file. But, to counter all these problems we have a professional tool like Data Recovery Freeware MBOX file converter. This MBOX to PST converter allow you to convert MBOX file into a number of file formats like PST, DOC, DOCX, HTML, MHTML, MBOX, PDF, etc. However, this tool migrates the MBOX file to a number of email clients like Office 365, Thunderbird, Yahoo Mail, IMAP, Gmail, etc. It also converts the MBOX file into bulk without damaging the MBOX  data. This amazing tool deletes the MBOX file on the basis of subject, from, to, body, etc. Many other additional features come with this tool. 

Steps to convert the MBOX file 

- Download and install the MBOX file converter.

- Then select the MBOX file to convert. 

- Now select the MBOX file/folder to convert. 

- After this select the file format to convert.

- Now set the path to save the button.

- Lastly, click on the convert button to start the conversion process.