Should I email my resume to an employer as a PDF attachment?
If an employer asks for a PDF version to be sent via email, then that's what you should do. However, if the employer does not ask specifically for a PDF attachment, the resume should be sent according to my E-Resume Guide, Emailing You Resume.
I realize that PDF resumes hold their formatting beautifully when sent as attachments, but the main problem is that attachments are often not opened because recipients worry about the transfer of viruses.
So the best route is still to copy and paste the Plain Text version of your resume into the body of an email. In the cover note, you might offer to snail mail a hardcopy version or to email a PDF, if the employer wishes.