found this which has a nice user experience but it requires images, doesn’t support pdf: https://emberbyte.itch.io/comic-reader-demo
another: https://akapen011.itch.io/how-to-make-a-browser-readable-comic-on-itchio
non-specific to itch:
- https://mozilla.github.io/pdf.js/
- https://pdfobject.com/guide/quick-start.html
- https://github.com/embedpdf/embed-pdf-viewer (great feature list but does not have good intro docs)