Is it possible to play this game using a PDF editor? And if so, which features does it need? (Especially if annotations suffice, that would make it easy to play over the internet as well)
Great question. The best play experience with this game is with the print edition, and the second best experience is with the print-and-play version.
The reason for this is that there are prompts that rely on the book being physical, requiring you to tear, burn, hit, throw the book, etc. Some of these prompts have additional significance in that when you tear the page, for example, it may reveal something on the next page. Likewise, if you pass on the book or play it again, those modifications matter for the subsequent playthrough.
Of course, if you want to play using a PDF editor, you're more than welcome to. But you will miss out on an important part of the experience. I'd say a PDF editor is best for folks who want to read SPINE but not necessarily play it.
I hope that helps! Feel free to follow up with additional questions.