.document-slider{margin:20px auto;}
.document-slider .slide-item{
    float: left;
    text-align: center;
    width: 25%;
}
.document-slider img{
    border:1px solid #dedede;
    transition: box-shadow 0.3s;
}
.document-slider img:hover {
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.4);
}