As a beta reader / reviewer, I totally agree with what Spectorium_1 and Darthmongoose say, however there are a few things I want to add to their points.
Okay, so I get that you're giving the reviewer dialogue to review but through that dialogue the reader is meant to see some type of story because you plan on creating a comic using this dialogue- correct me if I'm wrong. But if I'm assuming right, these 40 pages of dialogue are meant to be some type of script.
If so then I think you need to clarify this because some beta readers /reviewers will only review certain types of written work - i.e. only scripts or only novels etc.
Also with the clarification, people are going to need a little more information. Like what type of feedback are you looking for? Are you looking for feedback on plot, characters, dialogue, grammar and spelling etc. (I'm asking this based on my assumption that your dialogue is a script and that the dialogue is going to be an important part of your story telling.
Is the reviewer going to just read 40 page of dialogue, or have you put them into scenes / parts / panels so the reader can see actions and settings. Honestly, if it's just going to be dialogue, I don't think there are going to be a lot of reviewers who are going to be willing to read just dialogue and 40 pages of it.
Idk maybe I'm wrong but reading what's going on like having actions and settings between dialogue makes it easier to understand the dialogue and give feedback on it, but then again this might just be me.
Anyway, I would maybe suggest creating a collaboration post for a critique partner where both parties would beta read each others work. It could help with the whole 'trust' thing since you both will be sharing unpublished work. Also, most reviewers in the Reviews and Feedback category will review a part of someone else's work sometimes in exchange for feedback. Your request, however, really looks like something long-term and not just one quick review.
Honestly, I also don't mind doing this, but I need more clarification and information before I commit to something like this. And I'm sure there are a few more reviewers who feel the same way.