.at-pdf-viewer {
    width: 100%;
    max-width: 100%;
    height: auto;
    overflow: hidden;
    position: relative;
}

.at-pdf-viewer canvas {
    display: block;
    margin: 10px auto;
    width: 100% !important;   /* scale canvas to container width */
    height: auto !important;  /* maintain aspect ratio */
    box-shadow: 0 2px 8px rgba(0,0,0,0.1);
    border-radius: 4px;
}