Solution Proposal
The solution is to convert a file in SharePoint to PDF.
A new command as Convert-PnPFileToPDF
The command should accept the file url (mandatory) and the target location (as optional) where the file should be saved.
If target location isn't specified, the file will be saved in one drive.

Will be working on this, and creating a PR soon.

*Save to Local
*Retrieve as Memory Stream
*Upload to SharePoint Library
*CheckInType
*Publish
*Approve