Google-sheets – Track changes in read only shared Google Docs

@Pacerier's answer is correct — for a spreadsheet. For a word processing document or presentation, that menu does not exist.

As far as I have found, word processing and presentation documents provide notifications for updates to comments, but not the content of the document. Comment notifications seem to be enabled by default and can be changed by clicking the Comments button (next to the Share button, in the top right area of the page) and then Notification Settings.

• Go to https://www.google.com/dashboard/
• Select "Edit personal information"
• Change the "Nickname" field to what you want to appear in Google Docs
• Click "Save"

Note: it will take some time for the change to propagate. For me it took about 10 minutes, your mileage may vary.

Note2: I have tested this carefully, and this worked for me at the time this was written. However later on Google has made changes to Google Docs transitioning it to Google Drive. After this, the following anonymous comment has been received: "Google Account and Google Docs are independent of each other. This change has no effect." I'm suspecting that the author of the comment means Google Drive here, not Google Docs, and that the method above may no longer work.