Iwork documents not uploading from iPad to iCloud - despite strong wifi connection. Can they be forced to sync?

You could try disabling document and data syncing in the iCloud settings, then restarting your iPad and then re-enabling document and data syncing. However if the documents have become corrupt, there maybe nothing that you can do.

Whilst it won't help you recover documents that have already become corrupt, can I suggest you get into the habit ofbacking up your documents in the cloud regularly.