I've looked at hundreds or resumes. It can be worse than typos or grammar. That's minor in comparison. Dates missing, were you a Captain or FO(if you were FO and didn't say it were you trying to be misleading???), jobs missing, gaps in work history, how long did you fly a specific aircraft, etc.
The interview transitions from an interview to a resume investigation - "what dates? Which seat? When? Where? Why didn't you put that down?" The candidate loses any momentum they might have had. Instead of trying to connect, or tell their story, time is spent correcting their resume. You might recover but it's a bad start. The reverse of that is when the resume is done well. A guy sat down for his interview with HR " she grabs a pen and starts reading my resume. Starts to ticking off things on my resume 'well you've got everything we want to see.' At that point I realized 'you've got this." Obviously the interview process wasn't over but it was a great confidence boost for him to pass the first step with a pat on the back and no significant questions.
And here's the crazy part - people think their resumes tell the details, until you start asking questions. It's a total momentum suck when, instead of check marks, the resumes starts getting hand written corrections and additions. That's what you pay the money for, to maintain the momentum.
A guy asked me to review a resume for a guy he knew. He jump seated frequently with the guy. I told him it needed to be rewritten because a lot was missing. He insisted the resume was fine. "Ok, I'll ask questions and you look at the resume and tell me." It went downhill rapidly. From the resume he couldn't tell me what a/c the guy was currently flying, if he was Captain, when he upgraded, which a/c he'd flown as FO or CA, what he flown at previous jobs etc, etc. At first glance the resume looked fine until you realized a lot of details were missing.
And if a resume company says "you've done so much don't bother putting down the first half of your career" (true story!?) just walk away. That's terrible advice. Luckily he had two resumes and on one of them he'd ignored their advice.
I do not get any financial rewards from recommending having someone else look at your resume so I'm not trying to push any company or product. A buddy who works in hiring, or has in the past, should work. It's a fresh set of eyes during a detailed review. Guys feel bad about the typos but it's the missing details, or jobs, that can really hurt. No one gets suspicious of a typo, but missing job history might start the questioning and you might end up watching momentum walk out the door.