How to disable inline attachments on viewing incoming email

I am afraid it is not a joke. You can tell Mail to make all attachments an icon in your composition view, but it will not distinguish between PDF's and image files such as jpg or png, so everything will be viewed as an icon. Or you can tell Mail not to present the attachments as icons, in which case all one page PDF's and image files will be displayed in line, contents showing.

It is important to remember that this applies only when you are composing an email - it is your view as you write the email. How attachments are handled by the email program at the reception end is, of course, out of the control of Mac Mail. A little more control over how an email might look on the other end would be nice, but anything like that would involve creating standards that all email programs could adhere to. People who want emails to look a certain way, such as the emails you received from Apple, generally use html encoding, and it seems like most mail programs adhere to the same basic set of standards there.