This is a premium feature available with Astra Pro.
Make sure you have activated the module from Appearance > Astra Options > Spacing.
You will get options to set spacing for posts and pagination on blog/archive pages. You can find settings under Appearance > Customize > Blog > Blog / Archive.
Below are the available options-
Post Pagination Space
It will add padding around the pagination option from all sides.
It will add a margin to the individual post from all sides.
Post Inside Space
It will add padding for the individual post from all sides.