AC4 Black Flag - Back-up for save files

Create a new file using Notepad, add this line (just make sure it uses the path to your UPlay installation directory)
xcopy "<uplay_installation_directory>\Ubisoft Game Launcher\savegames\<your_uplay_id>\437" "C:\Backup\AC4BF" /Y /S
Save this file as a batch file, e.g backup_AC.bat
I use this line in my file:
xcopy "C:\Program Files (x86)\Ubisoft\Ubisoft Game Launcher\savegames\<my_uplay_id>\437" "C:/Saves/AC4BF" /Y /S
Just run the .bat file after you exit the game - you should now have a back-up of your files.
Using Radeon Pro (if you have an AMD video card) you can even run the .bat file automatically when you exit the game.
To automatically run the batch file from Radeon Pro, see the attached screenshot.