The main reason why many people use .pdf files is because it assures that the appearance of the document will be the same for all users, and it also permits mixing text and pictures in a reasonably standardized way. The Reader has always been free, so anyone (in theory at least) can just download it.

There has also been the belief that a .pdf file was a "safer" way to post stuff, since the main content is a "mostly binary" file and it was believed that it was unlikely malicious (executable) content could be added.

Adobe has found, though, that a couple of vulnerabilities exist in some versions of both the Readers and in the Acrobat (and possibly in the older Distiller) used to create .pdf files. The vulnerabilies that have been found are considered "serious" but thus far there have been no reports of anyone trying to use them. Unconfirmed but suggestive information indicates the vulnerabilities could only be used in a .pdf attached to an email, since the exploit apparently relies on other "content" arriving at the same time.

For Windows and MacOSX the problem is fixed in Reader version 6.03, so if you have an older one, you probably should update.

A slightly different vulnerability has been found in Reader version 5.0.9 for Unix.

FREE UPDATES should be available at Adobe Downloads. Click on the Reader for your OS.

John