You can use the bookmark manager of Fuxin Reader to add bookmarks and sub-bookmarks. Please refer to the following steps for specific operations. The demo software is Fuxin reader.

1. First, open the target PDF file with Fuxin reader on the computer, and click the bookmark management icon on the left.

2. Then drag the document to the specified page and click the Add Bookmark button.

3. Then name the bookmark, then drag the page to the position where it needs to be a child bookmark, add the bookmark again, and name it the same.

4. Then drag the contents of the child bookmark with the mouse to adjust to the target bookmark.

5. After completing the above settings, you can add bookmarks and sub-bookmarks to the reply reader.