You can adjust this setting so anyone with the link can view, comment, or edit the file. This setting works a lot like sending links to news articles or websites via email--if you’ve allowed anyone with the link to view the file, people who have the link will be able to access the file. This means that if the message is forwarded, or if new people are added to the conversation, those people will be able to access the file and won’t need a Google Account to view it.