I know how to save a document using the standard commands, but my point is that if the document is not closed, the changes are not actually saved. For example, I work on a document for several hours and command save. i open it on another computer from Dropbox, and none of my changes are there, and when I try to save it on another computer, I get conflicted copies. The same is true if the power goes out. The auto save function is just an automatic save command. Auto-save doesn't help in the circumstances I mentioned.

Ordinarily, you will be prompted to save if the document is in an unsaved state.
When you open a Dropbox file, the process is akin to opening a document attached to an email, in that Windows creates a temporary folder for it and the copy you open is saved to that temporary folder, not to Dropbox - which isn't supported by Office. If you want to avoid that grief, download the file, edit & save it, then upload the saved edit.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]