Remember the old days when we thought that Word documents were safe from viruses due to the assumption that they didn’t contain any piece of executable code? The sudden appearance of macro viruses proved us to be wrong back then.
It is also possible for aplication to automatically open a website using the browser if there are links contained within the PDF document. A couple of specially-crafted PDF documents has proven this for us. It is no question that this extended functionality would eventually bring about PDF document borne malware that can access URLs and download possibly malicious files into the affected system. A possible drawback here (on the side of the attackers, that is) is that the application issues a prompt first whether the user wants to proceed accessing the website. However, by utilizing social engineering, a creative attacker or malware author can succeed despite that security measure.