<p>Using JDK1.5 how does one send a binary attachemnt (such as a PDF file) easily using the JavaMail API?</p>

If you want to do it easily I'd suggest using
Commons-Email
! It's built on the JavaMail API, but it makes it much simpler.
There is a sample in the
User Guide
on how to send email with attachments... it's much easier than using the standard JavaMail API!