org-theme/scss/partials/_postamble.scss

#postamble {
    position:fixed;
    bottom:0;
    left:0;
    width: $toc-width;
    padding: 12px;
    color: $color-text-invert;
    background: $color-background-obscur;
    border-top: solid 10px #343131;
    font-family: $serif;
    font-size: 0.8em;
    z-index:400;

    .author {
        font-size: 1rem;
        margin-bottom: 0px;
    }

    .date {
        font-size: 0.9rem;
        margin-bottom: 0px;
        color: $color-secondary;
    }

    .creator, .validation {
        display:none;
    }
}