(How) does it handle CMYK and print PDFs? I see images of printed books created by Paged.js, were these post-processed, or printed using a printer that does a best-effort RGB conversion?
I'm not sure - we don't do color correction on our PDFs because we don't have photos in them and color rendering is not mission critical - but paged.js is focused on the concern of layout for print media. I would imagine color rendering can be solved orthogonally to what paged.js does for you, as long as you specify the color data in CSS. I'm pretty sure paged.js will pass it through without messing with it, so you're good if the browser that Playwright/puppeteer is driving supports the correct color profile when emitting the PDF. I honestly don't know if browsers have sufficient support for that when emitting a PDF, though.
Overall you're right that color correction is another area where you could probably command a premium.
It's certainly an area with more depth than I anticipated when I first started getting into it. Adobe is still pretty much the only one that can get a PDF compliant with print standards.
As far as I know, there's no way to currently get colors adhering to print color profiles in CMYK out of browsers.
Indeed, if color correctness isn't mission critical, I can imagine that going with Paged.js can be a nice experience!
(Edit: in my experience so far, it's been really really hard to 'correct' colors from an existing PDF in a way that gets a satisfying end result---the colors are usually muted/washed out)
You're right - although many of the building blocks are there, it appears there is no way to specify a colorspace or print profile when asking Chrome to emit a PDF (and I doubt the other browsers are any better). Skia (the PDF rendering engine that Chromium uses) actually supports colorspace transforms, but Chromium doesn't seem to hook that up to CSS or even support non-RGBA colors in its rendering pipeline.
