Put on hold = left until a later date ( usually used in the passive)
- Plans for building the extension have been put on hold until our finances are in a better state.
- He put his retirement on hold until he had found a solution.
- I am afraid that the whole matter is on hold just now.
On paper = when you read about it, it may seem OK , but might not turn out to be so.
- The plans look great on paper, but you never know quite how things will turn out , of course.