Can you please try with the latest version of ADE 4.0.3 Download | Adobe Digital Editions.
The menu items "Authorize Computer or Authorization Info" or "Ctrl+Shift+U or Ctrl+Shift+I" works when you are in Library mode. If you are in Reading mode, please click Library button to switch to Library mode.
Thanks for those tips.
I have downloaded and installed the latest version and chosen to 'authorize' an Adobe ID.
Behaviour remains the same. The ePUB version of the book downloads and works just fine; the PDF downloads and is blank aside from the contents pane.
The reason I want the PDF to work is because it is paginated as per the hard copy book; the ePUB's pagination is variable and so useless for referencing.
I see a lot of people have similar issues, invariably unsolved, so yet another pothole on the great Information Super Highway! Sigh.
Have you finally found a way of reading those books in pdf ? I have the exact same problem (but on Mac), and I can't seem to find a solution...