Did Cameron Crowe really misspell "neutral" in the screenplay? Wow. He's a writer.
But yeah, the typo are likely unintentional by Crowe - in the end this is just a prop, and as I mentioned automated spellcheckers were annoying back then.
on edit: the hippy night guy at the printer place seems literate, he read it, but guess what - he has the same silly spelling errors as Jerry!
Heck, Microsoft Word didn't have automatic spell checking (always working in the background) until 2003. If I recall correctly, even MS Word's spell checker wasn't developed in house, but the tech was originally licensed from Houghton-Mifflin in the early-to-mid-90s. I believe Word 7.0 had it, and possibly earlier versions, but it was still a "fairly new thing" in the early-to-mid-90s in the desktop space.