Two people are paying for the pattern, and they share ownership. That is fine. They can hand it back and forth and take turns using it. That is allowed. One of them could gift it to the other, still fine.
It is not legal to photocopy the pattern so that each of you has a copy -- that is copyright infringement. Likewise, you can't scan it and give the other person a file containing the pattern.
Where things get harder to define in the modern world is things like -- can you be at different locations but facetime and share the information in your coversation? I'd say yes, that's ok, because it's much like a phone call. But can you face time the pattern for the other person? Not sure, on that one. On the one hand, it's pretty much the same thing as being in the same room and holding the pattern up so your friend can see it, on the other hand, you're using a facsimile of it, but on the third hand, it's temporary in that facetime session and does not exist as a separate entity.
So to answer your original question -- it's not legal to photocopy it. It is legal to share it.