Modifying "Review" page

Hello, I’m using OJS 3, and would like to modify the “Review” page at workflow, so that it would generate a pdf file, containing the text of review, and attach it to the article.

What files and pages should I modify, where to start? Should I create my own classes, or I can use existing ones? Shall I do it as a plugin? Would it be simplier?

Thanks for answer!