It takes some reading and re-reading but look at this document, Permissions.
From my notes on the printout of that page I have this:
To allow a user to over-write a workbook they must have the following permissions:
1) Web Edit
2) Write/Web Save
3) Download/Web Save As
Web Edit is only for views (what a user sees in the browser when logged in to Server).
The permission "Download/Web Save As" allowes a user to download and then save the workbook (if they wish) as a new workbook on the server.
Quote from Who Can Edit and Create Views (you'll want to read and re-read this page, too)
"Note that to enable a user to overwrite a workbook you must grant all three of these permissions: Web Edit to enter edit mode, Download/Web Save As to make the Save and Save As commands available, and Write/Web Save to actually be able to overwrite the workbook."
Julia Hennelly wrote:
After spending a great deal of time playing around with permissions etc to set up the following environment. I thought I would share and also make sure I have not missed anything. We basically want a project for authors to work on templates I design
This Project would have "Download/Web Save As" permission so the workbook can be downloaded
and then want them to save those templates to another project to which the end users have access.
This other Project would have "Write/Web Save" permission. Not sure if it would require either of the other two...maybe "Download/Web Save As"?
Giving an author save and save as capabilities did NOT give them the rights to save a workbook they had to have publishing rights on the server. Is that correct - editor permissons is not enough to save the workbook?
Yes, having Publishing rights sounds logical.
Secondly Save and Save as work exactly the same at least that is how it appears to me and both options are shown even if only one option is selected in permissions - assume/hope that is planned to be fixed.
1) In summary to save an edited workbook a user needs to have publishing rights.
2) Turning off the save permission does not protect the original workbook from being overwritten.
Are these two statements true?
Your last two questions by my understanding:
1) I would guess true, however, I'm not in your situation so I haven't tested. I have Publishers and they are the only ones who can publish workbooks to the server.
2) The save permissions are for interacting with the workbook in the browser. If you have an author who is a Publisher then they can use Desktop to alter the workbook and publish directly to the server from Desktop and thus over-write the workbook (if they aren't paying attention this could be bad). I do this myself.
It's good you're experimenting with this. Letting us know your results helps others. If you are just having a devil of a time then contact support, they've been helpful for me.