I believe the content is the same. In the web document, sections 1-5 got put into sections 1.1 through 1.5, and then the remainder of the document picks up with section 2. In the PDF document sections 1-5 got put into sections 1 through 5, and the document continues at that point with section 6. This difference of 4 in section number I believe is the difference.
If this is of concern to you, you can file a bug.