You can send more than 10, but remember: quality is better than quantity. Don't overwhelm them with 200 pages as they will probably shred it (there have been stories like that). If you have a long history of communication, it's better to cover it as long as you can (I mean in years, not in a number of pages). Include one page per month if you have 2+ years of chats. If less than that, include 2 pages per month. Show how you and your partner talk on different topics, don't send only "good morning"s and "I love you"s.
Here's the great article advising how to include more proof to your application so it won't be shredded
https://www.linkedin.com/pulse/picture-worth-thousand-words-importance-photographic-evidence-carey Take a look at the part where they're talking about IMM 5532 form.