Need help adding a summary feature to sharepoint library

I currently have a library with a bunch of documents and want to add a feature that lets users read a brief (around 500 characters) summary of the file before they open it. The character limit to multi line text column is only 250 characters, is there a way for me to up that limit? Best case scenario would be a mouseover pop up bubble but if thats not possible, the standard column view would also work. Thanks in advance!