I recently dealt with that in my home. The popcorn, when it gets, gets loose and can come down. If you don't want it, just spray with water and get a scraper. It will be messy. In that room I chose to remove it.
To keep it up, yes--there is a spray at the big boxes that will patch it. What worked for me was to get an oil based primer and put a coat on the other rooms. This did not wet the popcorn and sealed it, so that my latex ceiling paint did not make the stuff come down.