This feature is designed for reading an article in a newspaper or magazine PDF:
In PDFs, articles are optional electronic threads that the PDF author may define within that PDF. Articles lead readers through the PDF content, jumping over pages or areas of the page that are not included in the article, in the same way that you might skim through a traditional newspaper or magazine, following one specific story and ignoring the rest. When you read an article, the page view may zoom in or out so that the current part of the article fills the screen.
To disable the Hand tool from following an article path, go to the the Edit menu and choose Preferences. In the General category, uncheck "Make Hand tool read articles".