How can I find an editor to check my short film script?

I'm going to make some assumptions here. I assume you're not asking for grammar or spelling checking. Or formatting. There are software applications that can check all that. I personally wrote a screenplay and wrote my own software formatting and checking software in an old printing language for the original Unix OS. There are tons of better packages out there today.

I'm going to make the assumption that you're not asking about writing dynamics or organization or screenplay advice. There are many books on that subject, and a few that are touted as the best. One uses the organization of the movie screenplay for Butch Cassidy and the Sundance Kid. Or Chinatown. Beautiful books and pretty cool to read.

I'm going to assume that you're asking the question that thousands of new writers ask. "How can I get my work read?" I'll tell you what I know.

First, you'll be told to look for an agent. There are books that list agents and agencies on line. In my experience, however, there are agents who will read your stuff and promise to do something with it and are simply not good at their job. There are publishing houses that will not take unsolicited manuscripts for a variety of reasons. And they really mean it, so don't bother. There are publishing houses that will accept manuscripts and are actually interested in your paying them money to publish or otherwise distribute your work. There's also Amazon, which will not only publish your stuff, but get you paid a bit for what gets sold. In this, your own work is what's being tested, because anyone can publish something bad and be ignored. But quality will out.

What you really want to do is make contacts. Go to movie fairs and screenings and work with movie productions, look for opportunities to work on set or even be an extra. Beward, tho', these folks are used to being pestered by everyone. There's a great quote in the Kevin Bacon movie, The Big Picture, where the character says, "But I'm actually a movie producer (or something like that)" and the restaurant owner says, "Oh, cool -- my busboy's a movie producer!" So the message here is that there's a lot of competition, and while that may sound negative, the fact is that it forces people to be really, really good at this to succeed.

So my advice to you is to keep doing all that grunt work to distribute, get better at your craft and keep asking for advice from a lot of people who may ignore you. But if you get out in the world and keep trying to make contacts in all aspects of whatever entertainment medium(s) you are interested, you can be very frustrated or you can cherish that rare bit of input you get from someone.

I recall submitting a short story to a publisher and I got a rejection, but it came with a note telling me how to improve my piece. That rejection was actually more valuable to me than the eventual publishing I got. Some folks are in the business because they love it more than they love their own success, and are genuinely interested in seeing great talent be developed. You can take advantage of this. But you need to go out and ask.

There are a number of Screenplay formatting software out there that will ensure your script is in the correct format. Mac offers a free app called Highland that has gotten much notoriety. There are many script editor services out there however keep in mind really good one are expensive and far and few apart. The Hollywood reporter covered this very topic here https://www.hollywoodreporter.com/news/why-are-wannabe-screenwriters-getting-scammed-1130919. Once you have edited your story you can try entering your story in a screen writing contest, here is a list of some contests of note. https://www.moviebytes.com/best-screenwriting-contests.cfm . Even if your script does not win you will probably get invaluable feed back .