The Autosave feature guards against losing your work in case of a power failure by incrementally, and at regular intervals, saving file changes to a specified location. The original file is not modified. Instead, Acrobat creates an autosave file of changes, which includes all the changes you made to the open file since the last automatic save. The amount of new information that the autosave file contains depends on how frequently Acrobat saves the autosave file. If you set the autosave interval to 15 minutes, you could lose the last 14 minutes of your work if a problem occurs. Frequent automatic saving prevents loss of data, and is especially useful if you make extensive changes to a document, such as by adding comments.
You can apply autosave changes to the original files when you restart Acrobat. When you close, save manually, or revert to the last-saved version of a file, the autosave file is deleted.
For more information, please check the help page https://helpx.adobe.com/acrobat/using/saving-pdfs.html#about_the_autosave_feature
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