Function overlay 

pub fn overlay<R: Resolve>(
    page: &mut Page,
    page_dict: &Dict,
    catalog: &Dict,
    r: &R,
    ctx: &mut BuildContext,
    limits: &Limits,
    diags: &mut Diagnostics,
)

Appends every visible annotation’s appearance to a built page.

The page’s own resources are the fallback for an appearance form that declares none, so a form with no /Resources of its own resolves names against the page.