@intrepidhero LiquidText on an iPad is my go-to. There is a Windows version but I dont use it that way. I like the iPad because I can use my Apple Pencil to select and highlight although I still type in comments. See here: https://www.liquidtext.net/
I also use Nebo on my iPad to hand write notes (turns them into text) but you can import PDFs and write directly on the document. I’ve only played with this a little bit but I use Nebo all the time for taking notes and writing. https://www.nebo.app/
@mstine Yes, I can see why you say that, and I'm guessing it's just a matter of time before we'll be able to create a Canvas that has a PDF on it that you can then annotate in a way that integrates with all the other stuff you have in Obsidian.
I love #LiquidText and #Marginnote, but despite using both for a couple of small projects, they feel too cramped for me. I think I won't use apps like those until they are turned into Minority Report–like augmented reality apps.