PDF documents can be huge if they're embedded with print-quality images and the PDF document is designed for commercial printing. Although Adobe Reader 8 is faster than previous versions, it can still take a while to open...and that's before you open your PDF document.
Try Foxit PDF Reader 2 and see if makes a difference on your system.
Cotton seedling freezes to death as Chang'e-4 shuts down for the Moon's 14-day lunar night
Fortnite easily out-earns PUBG, Assassin's Creed Odyssey and Red Dead Redemption 2 in 2018
Meteor showers as a service will be visible for about 100 kilometres in all directions
Saturn's rings only formed in the past 100 million years, suggests analysis of Cassini space probe data
New findings contradict conventional belief that Saturn's rings were formed along with the planet about 4.5 billion years ago