Personalizar tamaño texto en títulos y encabezados

You can customize the default header sizes by adding something like the below to the "Custom HTML Head Content" setting: 

 <style>

.page-content h1 { font-size: 2rem; }

.page-content h2 { font-size: 1.8rem; }

.page-content h3 { font-size: 1.6rem; }

.page-content h4 { font-size: 1.4rem; }

.page-content h5 { font-size: 1.3rem; }

.page-content h6 { font-size: 1.15rem; }

</style> 

 https://github.com/BookStackApp/BookStack/issues/462#issuecomment-786803638