Stop Mail from previewing pdfs and images in the body of an email Is there a way in the Mail.app to prevent it from previewing pdfs and images in the body of an email. 

So that instead you just a get a normal file attachment ?
It seems that the display of images (including PDF documents) can be disabled using this Terminal command:

defaults write com.apple.mail DisableInlineAttachmentViewing 1


The display of images/PDFs can be re-enabled by using this command:

defaults write com.apple.mail DisableInlineAttachmentViewing 0