Benoît,

I'm ot sure this will work and I don't see any Windows 8 drivers listed. You can try...

First run Delete Print Jobs to remove any stuck print job in the queue.

Disconnect the printer.

Download and run the patch(printer cleanup utility) until it prompts you to restart your computer.

Restart your computer. Make sure the printer is removed. Manual Printer Driver Removal

Download the Vista 32-bit drivers for Windows 8 32-bit or the Vista 64-bit drivers for Windows 8 64-bit. Install the Vista drivers in the Vista SP2 Compatibility mode You'll get a message, the printer is not connected. Connect the printer at this time(powered on).

Links to the patch/drivers can be found at...

Dell 720 Color Inkjet Printer owners thread (W7)

Remember virus programs and firewalls will block communications. If you're using Windows Defender, they these instructions as they should be similar...

Allow Printer past Microsoft Essentials

Rick