When making a movie pitch, do you need to have a screenplay or are there other types of documents you can have instead? Sometimes, I would assume someone would pitch general ideas and worldbuilding ideas instead of a screenplay, so I am wondering if this is common or studios never buys a movie pitch if the person doesn't already have a screenplay at hand.
There is the exception of animation films where storyboards seem to work instead of a screenplay, but in all other cases you need one.
During a short elevator pitch you only present the idea of the film, what makes it special and a few other interesting details. However, in case the potential investor asks you whether they can read the script, there is only one acceptable answer: "Sure, I've got a copy with me, here it is." Even if you can excuse yourself and promise to send the script later and they are still interested, there will be a follow-up meeting in the near future where you deliver the full sales pitch package. You need to be convincing, provide details, include a budget estimation, and answer all kind of difficult questions. Without having written the complete screenplay, you will fail. Also, you should hand everyone a copy of the script at the end of the meeting. There is no way around that.
Think about the message you would send if you cannot offer a script. If you are not willing to invest your time into writing the screenplay first, people will think that you're not confident about your project. Why should they take the risk to invest money, then?
This may sound a bit harsh, but ideas alone are worthless, because anybody can come up with great ideas. Studios are looking for more tangible things: a screenplay or storyboards for animation are a must, maybe a short film as proof of concept, and they want people that are easy to work with and who are enthusiastic about the project. That's the package you need to sell.