Do not use plain text in the sense of .txt or even .md. Do use plain text in the sense that the text should be formatted but there should be no graphics except (optionally) the occasional horizontal rule or (if you have a strong enough graphic design background) a vertical rule dividing a sidebar.
Do distribute as PDF instead of MS Word or equivalent.
I have a background as a visual designer, so this is good advice. I used to have very visual resumes because it fit the field, but I'm realizing that would be not such a great thing in engineering.
Do distribute as PDF instead of MS Word or equivalent.