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With Marked, yes. You can write your own CSS styles, which carry over to the PDF.

Cool. Before I drop a huge (!!) $3.99 on this app, any idea whether the text in the PDF is selectable?

Definitely. Here's my (outdated) resume for reference: https://www.dropbox.com/s/r9m2j0msphbwdmq/resume.pdf

Very. Cool. Thank you :D