The reading for 添 is what you'd expect. The reading for 付 is the on'yomi reading, which you've never learned. It's ふ, but for this word it becomes ぷ from the rendaku fairies. Just think of an attachment where instead of a document or something, you get an attachment of poop (ぷ). What a gross attachment. Your friend who likes to send poop attachments is dumb.
Dear hiring manager, please have a look at the resume attached to this email. Thank you for your time.