html, body { min-height: 100%; }
.preview-card { position: sticky; top: 1rem; }
#pdfPreview {
    display: block;
    width: 100%;
    height: calc(100vh - 7.5rem);
    min-height: 720px;
    border: 0;
    background: #525659;
}
@media (max-width: 1199.98px) {
    .preview-card { position: static; }
    #pdfPreview { height: 900px; }
}