/* make full-height flex column so footer stays bottom */
html,
body {
    height: 100%;
    margin: 0;
}

body {
    display: flex;
    flex-direction: column;
    font-family: Arial, sans-serif;
}

header {
    background-color: #4CAF50;
    color: #fff;
    padding: 10px 20px;
    text-align: center;
}

nav {
    background-color: #333;
}

nav a {
    float: left;
    display: block;
    color: #fff;
    padding: 14px 20px;
    text-decoration: none;
}

nav a:hover {
    background-color: #ddd;
    color: #000;
}

/* this is now your “card” */
.content {
    flex: 1;
    background-color: #ddd;
    position: centre;
    margin-block: 20px 15px 10px 20px;
    padding: 20px;
    border-radius: 5px;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.1);
    max-width: 100%;
    margin: 20px 10px;
}

footer {
    background-color: #4CAF50;
    color: #fff;
    text-align: center;
    padding: 10px 20px;
}

/* make the PDF viewer fill the card */
.content iframe {
    display: block;
    /* remove inline-block whitespace issues */
    width: 100%;
    /* full width of .content */
    height: 600px;
    /* or whatever height you prefer */
    border: none;
    /* get rid of the default border */
}