I'd forgotten DropBox made a few changes in the last few months.
When you open you DropBox account it's like looking at a specially set out folder where you can create new folders and sub-folders within in it, and place files where you like in it.
In the file/folder list within any folder there's a box on the left and when you click on that ti highlight a file or folder without opening it there are two buttons appear on the right, one says 'Share' and looks like an oval with a square in it - clicking the oval will take you into the folder or the file. Near the top right corner is another button that says 'Share' - click on either share button opens the 'Sharing' windows which is like an email form. Where it says 'To' you enter the email address of someone if you want them and individual to have access whenever they log in - you can enter multiple email addresses for a group of people. On the right of that line is a button that is set to a default of 'Can Edit' you can open that an change it to 'Can view' if you want - this allows them to view, download, and comment on it while 'Can edit' allows them to edit, delete, comment, and add to their DropBox a/c.
Below that is a link 'Create a link' which allows you to create a link to that file which will allow anyone who uses the link to view the folder and it's content - you then send that link to whoever you wish.
In the two link I gave earlier one is such a link to a specific file and one is to a folder, so you can see how versatile the system is. I have a couple of folders I share with my editors on the 'Can View' option so they can look at the files, download them to their home computer, and work on them. Then they send me to amended file for me to go through before I add what I like of their edits to the master file, and later upload a replacement file to DropBox. This method gives me total control of the version in DropBox while allowing them to see what I'm working on.
My brother uses his editor access to edit my works in progress when he gets bored with nothing else to do - which means he gets to read and work on the story before I finish it when he does that.
Another thing, DropBox sends all those with a direct Share access an email when there's a change to the shared folder / file and they send you a security email when you log in without using the cookie saved from the last access.