Difference between "Save" and "Save as"

Hi,

There is no difference between "Save" and "Save as" option in Adobe Reader DC. Ideally, when we click the "Save" button it should not ask for any location, but it did ask for location. I am not sure why Adobe Reader DC behave like this? Anybody has an answer to my question and suggestion to avoid this.

Adobe Reader version 2019.012.20035

Thanks,

Siva