But a side effect of the "feature" is that Outlook Express defaults to deny access to PDF files, prompting some to suspect there's an ulterior motive along the line somewhere.
Microsoft has had its beady eye on Adobe for quite a while, and is understandably miffed that Adobe and the PDF format is so widely accepted.
It has its own XDOCS specification but it will take a while for that to be successful, if it ever is.
It pays to be paranoid in this business, as Intel's Andy Grove memorably said one, and now there's a few people getting paranoid about the PDF blockage.
Here in the Adobe forums you'll find some more dicussion about this.
You can get round the default setting, as some of these messages explain. µ