Hi, before i start i know there is a very simple answer to this! It is to download the attachment.
But just i just wanted to see if anyone else had users reporting the same issue:
Our users say they used to be able to copy from say Excel documents that had been attached to tickets and then paste into another document etc. Now Preview changes the text of the document, and will not allow copying in that it appears to alter the formatting of the text when copied and pasted.
Disclaimer: I dont know if something has changed in the way Jira renders previews or if it has always been like this (i have never paid too much attention to it)