I've fixed your question so that it accurately represents what I said and doesn't put words in my mouth.
If I click on a link and download a document, is that illegal?
I do not know if the person has the right to distribute it or not. IANAL, but when people were getting sued by the RIAA years back, it was never about downloading, but also distribution.
As I said, IANAL, but feel free to correct me, but my understanding is that downloading a document from the internet is not illegal.
Did you mean to write "but about distribution" here?
After all, illegally downloading research papers in order to write new ones is highly transformative.