Having abandoned my search for an easy way to save pdfs to Diigo, it happened accidentally by just using Chrome. Chrome opens pdfs inside a browser tab, where my Diigolet works comfortably. However, there are some problems.
The biggest is that I cannot highlight. So I can save but not annotate. When I try, this happens:
Also, it can’t grab the title of the work, so I have to title it manually.
But it’s a step in the right direction, I think.