You'll lose all of the undo history for a file when you close the file.
Explanation:
You'll lose all of the undo history for a file when you close the file. When you're working on a file on you computer you have the possibility of going back if you make a mistake. This applies to design software (for example, the Adobe programs such as Photoshop or Illustrator) and also to text and calculation softwares (Word or Excel). You can go back many steps and rearrange your work many times. However, once you close you file you lose the undo history and will only have the last changes you saved.
