Multi-pass reading
Skim the paper first, skipping over anything that would take much mental effort. Just get an idea of where the paper is going, why it was written, what's old hat and what's new to you. To force yourself to keep moving, give yourself a limited time budget per page or use the autoscroll feature of your PDF reader.
Now, assuming the paper still seems worthwhile, go back and read the whole thing more carefully.
Why not practice on this webpage? Go ahead, skim it first.