Convert attachment to PDF

I am trying to find out how to convert a file in the Record Link to PDF, but can't find any solution. The customer adds a file to the notes of a sales order, it maybe an image file, but they don't want to covert it to PDF before attaching it email as the file as it is populated from Integration.  I can't work out how to covert it to PDF before attaching it to PDF before sending the email.  I have done the modification that attaches the files from the notes of the sales order. 

Any help/suggestions would be really appreciated.