Use lopdf to add bookmarks to PDF file in Rust

main.rs

use lopdf::{Bookmark, Document, Object};

fn main() {
    let mut doc = Document::load("input.pdf").unwrap();

    let pages = doc.get_pages();
    let page_3_obj = pages.get(&3).unwrap().clone();
    let _bm = doc.add_bookmark(
        Bookmark::new("Test Bookmark Title".into(), [0., 0., 1.], 0, page_3_obj),
        None,
    );

    let catalog_obj_id = doc
        .objects
        .iter()
        .find(|(_, obj)| obj.type_name().unwrap_or("") == "Catalog")
        .map(|(&id, _)| id)
        .unwrap();
    let outline = doc.build_outline().unwrap();
    let co = doc.get_object_mut(catalog_obj_id).unwrap();
    if let Object::Dictionary(ref mut dict) = co {
        dict.set("Outlines", Object::Reference(outline));
    }

    doc.save("output.pdf").unwrap();
}