That looks like a pretty heavy-weight solution, with a lot of complexity, and I don't mean that as a criticism at all. I'm not a 'go' developer myself. I've always wanted a pure JS solution (as a browser extension, maximum of 200 lines of code) that can capture the content of a web page (doing a virtual scroll to the bottom, to capture the whole page). Since there's no perfect way to translate HTML to PDF, my idea had always been to capture the IMAGE of the page (aside from capturing keywords for DB indexing which can be done separately just for 'search' support later on).

The fly in the ointment is of course the scrolling too, because some apps have "infinite" scrolling, and so in many SPAs there's literally no such thing as "The whole page". Anway, I haven't tried your app yet, because of not-JS and not-Small, reasons, but I'm just sharing my perspective on this topic. Thanks for sharing your project!