Altering size of text and spacing between navigation boxes

I want to alter the green navigation boxes at the bottom of the page. These are the PREVIOUS and NEXT boxes that I have made green with white text. They are just below the post box:

http://forgottenbutrelevant.com/2016/07/20/power-kills-democracy-as-a-method-of-nonviolence-by-r-j-rummel/

If you see, the boxes are up against eachother. Can you please provide me with CSS that will
1.) Make the text inside the boxes smaller.
2.) Create some space between them.

Hello,

Here is the css code:

.post-navigation .nav-previous, .post-navigation .nav-next, .paging-navigation .nav-previous, .paging-navigation .nav-next {
    font-size: 12px;
    max-width: 45%;
}

Regards,
Awan