I’ve created a new user account on my computer and want to access an existing Scrivener document through that account. I changed permissions on the Scrivener file to give read-write permission to this new user account but I keep getting the message that it’s a read-only file. I saw a thread here that tried to address this issue using Terminal but it veered in another direction. When I follow the basic instructions from that discussion, I get a Terminal message that the file doesn’t exist, so I assume I’m not putting in the file address correctly. Can you help?
The easiest way to make sure you have the correct file path typed in in Terminal is to not type it at all. 
Try typing in up to the point where you need to specify the file name, make sure there is a space entered on the end, and then drag the file from Finder into the Terminal window. It will paste the full path to that file and you can either type in the rest of the command, if necessary, or press return at that point.
Another way of doing this, if the file is okay to have public to the entire computer, is to place it in the Shared folder one level up from your user folder. This folder can be read and written by everyone that uses the computer though, so if you just want to share it between two accounts and not others, that isn’t a solution.