You can choose to add emails to an existing PDF file, instead of creating new. Just go to Email to PDF toolbar and click ‘Append to existing PDF’.
1. Select the emails and under Email to PDF toolbar, click ‘Append to existing PDF‘.
2. In the Open Dialog box, select the PDF file to which the selected emails will be added to. And Click Open.
3. The PDF file should have the selected emails appended starting from the last page of the PDF file.