SQLDev version: 18.104.22.168, Windows XP
Select some table -> right-click Open -> select "Data" tab -> pressing keys "Page Up", "Page Down" doesn't work.
The same is with "Columns" tab (you can check if you have a table with a dozens of columns)
A little different behaviour is on the "Constraints" tab: "Page Up", "Page Down" scrolls content only one row up or down.
Thanks for the report!
Fixed. Will be available next release.