I think using automatic software, like
CubexSoft EML to PDF Converter, is the safest option. The program facilitates bulk conversion without causing the attachments to be lost. A straightforward tool for both technical and non-technical users. The program is compatible with several popular email clients, such as Thunderbird, Apple Mail, Windows Live Mail, Entourage, and Outlook Express. When converting EML attachments to PDF, the application offers a number of sophisticated choices. The application has no file size restrictions, regardless of how many files users want to convert. compatible with all Mac OS and Windows versions.