We are sorry for the trouble. As described the subject of the email does not appear in the PDF when you convert the email to PDF
We tried to reproduce the issue on our end and its working fine and including the subject as well in the PDF file.
Would you mind sharing the steps you are doing to create the PDF file from Outlook? Also what is the version of the Adobe Acrobat 2017 you are using? To check the version go to Help > About Adobe Acrobat.
Also, make sure you have the latest version 17.11.30175 installed. Go to Help > Check for Updates.
If it still doesn't work, please try to repair the isntallation (for Windows Only) go to Help > Repair Installation.