Answer
Situation:
The Foxit PDF Editor /Reader doesn't prompt "Do you want to close all tabs or the current tab?" when I close it,it closed all of PDF files directly.
Solution:
If Foxit PDF Editor closes all tabs without prompting you to choose between closing all tabs or just the current tab when you close the program, it may be because the setting "Don't display a prompt before closing all tabs" is enabled in your Foxit PDF Editor program. To enable the prompt again, follow these steps: Go to the "File" tab > "Preferences" > "Documents" and check the option "Display a prompt before closing all tabs". Click on "OK" to save the setting.
After making the above setting, the next time you close Foxit PDF Editor/Foxit PDF Reader, a window will prompt you with "Do you want to close all tabs or the current tab".
In this window, if you choose the "Close all tabs" button, all files in all tabs will be closed. If you select the "Close current tab" button, only the PDF file in the current tab will be closed.