For best SEO value, what type of document/format should we put downloadable content?

Curious to see what the communities thoughts are In my case the downloadable content is a Q&A sheet a homeowner fills out after they have had a service done to their home. Helps them to avoid getting scammed by crappy service providers.

But what type of doc/format is best for what type of content? Anyone had luck with one type or another?

Any advice on-doc SEO guidance for the writer?
Any advice on-doc SEO markup?