Bill, the only way to do this (legitimately) is to find the older version on your PC if it still exists.
When iTunes replaces an old app with a new version it will typically move the old one to your Trash / Recycle Bin. Your first port of call is therefore to check in there to see if you can see an old copy. (if you are not using iTunes on a PC to manage your iPad you are completely out of luck).
If you do find an old version in the trash, try the following...
1) Remove / Delete the App from your iPad by holding the icon until it wiggles and then press the "x"
2) Open iTunes on your PC, switch to the "Apps" section in the left had navigation pane
3) Find the app in question, right click it, and choose "Delete" (now you have deleted the new version you don't want)
4) Restore the old version from your trash (there will be two in there now, the old and the new one, so take care to get the right one), which will place it back in iTunes
5) Sync your iPad and the old version will be installed.
Hope that helps.