After import PDF files or images to Flipfab PDF to flash flipping book converter, find the Language Setting on the right side of flipbook maker interface.
Click the circle icon on the right side to open the below window:
Here are 8 languages for you to choose. Check the ones you want, click OK and then check the above Switchable option. If there isn't the language you need, click Add button to edit new languages.
After publshing, readers can click the Switch Language icon to change languages of toolbar text conveniently while reading your flipbook.