If you have more than one computer and one is too old to update to latest versions, DO NOT UPDATE anything if you want to keep using the older computer. Tried to update existing iWork files on older computer with software version that created them and get messages that must update iWork software, but older computer can't be updated.
After hour go around with Apple Support it seems the problem is that I use iCloud to sync between my computers and iPads, which is supposed to be one of the advantages of Apple and I unknowingly updated software on a newer computer and even though I never touched these files with the newer computer I now cannot edit them on the older computer. What a bummer.
The reason for two computers of course is there are two people working and we weren't ready to upgrade hardware on both. The only alternative offered was to work directly with the web version.