Learn Spanish (Latin America): ¿Usted lee el libro aquí, señor?

The word for "you" here is usted, which is the formal version used to show respect (which fits perfectly with calling him señor!). In Spanish, usted always uses the exact same verb endings as "he" or "she" (él or ella). For a regular -er verb like leer (to read), you drop the -er and add -e, giving us lee. You would only use lees with the informal "you", tú.

Why is there no word for "Do" in the Spanish sentence?

Spanish doesn't use helping words like "do" or "does" to ask questions. You simply take the normal statement structure (Usted lee... meaning "You read...") and frame it with the upside-down and regular question marks (¿ and ?), raising your pitch at the end of the sentence when speaking.

I learned that titles need words like el or la before them. Why is it just señor at the end, not el señor?

You only need to add el or la before a title when you are talking about a person (for example: El señor lee el libro - The gentleman reads the book). Because you are talking directly to him in this sentence, you drop the el and just say señor.