If you want to display Chinese character in the PDF when you print your invoice, you will have to customize the font face before you can see the correct outcome.
1. Click on the Customize icon on the top right corner when you land on the Print Preview page.
2. From the top menu, switch to For All Document tab and lookup for Font Face. Change it to SongMing.
3. Finally, click Save at the end of the dialog box to update your changes.