For navigating first page and last pages of a pdf file, there is no keyboard shortcut like other PDF readers. It's a simple yet intuitive functionality for any PDF reader.
Generally ctrl+End, End are used to jump to the last page while ctrl+Home, Home are used to jump to the first page.
I've written a patch for this.
In View menu, two new entry is added i.e "First page", "Last Page" along with keyboard shortcuts. And view menu items are made responsive e.g. when I'm in the first page "previous page" and "first page" menu entries are disabled.