Mike - As suspected it's not outlook at fault.
I suspect your file is actually called
C:\PDF\CreateCARIAccount.pdf.pdf
or something similar! Open your file explorer and make sure that you have it set to display file extensions, or as M$ nicely call it "Hide known file extensions"
Then either rename it to the correct file or move it to somewhere in your documents and try again after changing the variable path to wherever you move it to.