Note
Markdown to PDF is a free service but beware that the file you use is going to be uploaded on a server. Due to it's simple nature of just getting a file and converting it into a PDF, the file is processed on the said server.
The server does delete the uploaded and processed files every 5 minutes, so it's both accessible and keeps server and storage costs to a minimum.
For security purposes, it is better if you self host this if you wish to use it for more critical markdown documents.