When I go into a Google Drive (gdoc) document, select some text, then go to my Text Messaging to paste it, I get a "File Cannot be Attached," error message.
When I copy and paste from anything else, it works fine.
Welcome to Android Central! When you're trying to paste, are you tapping that paper clip icon, or are you long-pressing in the text entry field until you see the Paste command come up? Do the latter.