@Dutch First, I would encourage you NOT to try to mimic what a regular word processor can do. The web is different. That said, what does come closest is what @peterdanckwerts suggests: the Scribe stack. You can learn more here: https://demo.bigwhiteduck.com/scribe/
Scribe is a nifty stack. But it requires that you learn how to write using markdown (a very simplified way to write HTML). This is a good thing! Markdown is wonderful and it will likely only take you 30 to 60 minutes to learn it. But there is some small adaptation/learning on your part.
As for the PDF … I’m not fully understanding the situation. Basically if something can be seen on a web page it can be downloaded. That’s the simple answer. So the real choices are:
- can I make it harder for someone to download? (answer: yes)
- can I hide the PDF from people except under special circumstances (answer: yes)
What is confusing me a bit in your question is in regards to how are you using the PDF? Are you using it somewhat like an image on a page? Embedded on a page? Something else? Tell us a bit more, or show us a bit more (URL link), and we can help you out.