By default, PDF bookmarks aren't automatically added to your document. First of all, PDFreactor must be configured to do so:

pdfReactor.setAddBookmarks(true);

When the default XHTML mode is enabled, the following bookmark levels are applied by default:

h1 { -ro-pdf-bookmark-level: 1;}
h2 { -ro-pdf-bookmark-level: 2;}
h3 { -ro-pdf-bookmark-level: 3;}
h4 { -ro-pdf-bookmark-level: 4;}
h5 { -ro-pdf-bookmark-level: 5;}
h6 { -ro-pdf-bookmark-level: 6;}

Using the -ro-pdf-bookmark-level style you can create bookmarks which link to arbitrary XML elements in your PDF files.

element { -ro-pdf-bookmark-level: 1 }

Using this property, one can structure the specified elements within the bookmark view of the PDF viewer. The elements are ordered in ascending order. The element with the lowest bookmark level is on top of the bookmark hierarchy (similar to HTML headlines). Several bookmark levels can be set using the -ro-pdf-bookmark-level style.