I think that most of what I proofread & polish the English of (it's almost all translations from Japanese) probably never touches paper. It sits on servers as web pages, or downloadable PDFs, or is a presentation for one-off use, e.g. at a conference. Spellcheckers have greatly reduced one part of the proofreaders task, & I don't really get asked to do layout correction. I think the customers mostly do that themselves, or for corporate brochures & the like send the final text back to whoever did the design to fit in. But people called proofreaders have had their job expand into copy editing.