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.