Checks if the PDF supports sub-page navigation, i.e. the possibility to navigate from one layer to another layer on the same page.
Sub-page navigation support is not desired in documents for print.
Page navigation allows you to navigate from one page to another, whereas sub-page navigation allows you to navigate from one layer to another layer on the same page.
Suppose you have a single page PDF showing the slides of a presentation. Each slide is on a different layer. When the user presses the forward arrow, the next slide (on the same page, but on another layer) is shown and the previous one (on another layer) is hidden.