To download Yahoo emails to PDF in bulk using the BitRecover Yahoo Backup Tool, you'll need to use the software's built-in functionality. First, you install and launch the tool on your computer. You then log in with your Yahoo email address and an app password, which provides a secure connection. The tool will display all your mailbox folders, and you can select the folders you want to convert to PDF. After choosing your folders, you simply select "PDF" from the list of available saving formats. The software will then process your selected emails, converting them into individual PDF files.