No messages are in pdf-format. I guess you mean you have received a message
with a pdf-attachment?
In that case, make sure you have Adobe Reader installed so that you can open
it. If printing doesn't work for you in Adobe Reader, contact Adobe support
as Outlook is no longer involved then.
Note that pdf-files can have restrictions imposed on them. For instance,
that you are unable to copy text out of it or that you cannot print it. If
you want to restrictions lifted, you'll have to contact the creator or
sender of the pdf-file and ask him/her to do so.