When I attach a pdf to an email in Outlook, a large PDF icon appears right next to the text (usually the greeting) in the body of the email. It used to be a smaller, more condensed version that ran along the top of the email. How to fix?.

Mac or Windows? I find this happens on my Mac. Usually, Windows will always attach. 

That usually happens if Outlook is inserting the PDF inline instead of as a regular attachment. Try attaching the file using Attach File rather than dragging it into the email. If it only started recently, it may also be due to a recent Outlook or Adobe update. Restarting Outlook and checking for updates is worth a try too.