Yes you can. I believe all you have to do is click the button 'Switch to Full Reply Screen' and then click the link File Manager, click 'chose file' to browse to the pdf file and select it. Then click 'Add file' to add it to TM. Add any comments to the text box. When done click 'Done Adding files'.
I think it comes up as a link.
Others, please correct me if I am wrong.
Cheers,
