This issue is result of a fairly long discussion on User mail list titled 'read
only document' that begins here
http://www.openoffice.org/servlets/ReadMsg?list=users&msgNo=163686

The request is to enhance interface with regard to document signing so average
user who won't RTFM and won't find a support list can 'learn by doing' that
signing a document makes changes to the document immediately detectable and can
be better and more reliable than assigning a 'read only' password as is
available in other products with proprietary file formats.

Proposed...
o In the signature message area of the UI (7th from left at bottom of app
window?) if a document is unsigned change content of message area so it is not
blank, e.g. bright bold red exclamation mark.
o When mouse is positioned over exclamation mark change hover text to something
similar to 'The document is not signed. To detect changes the document must be
signed.'
o Modify the Tools|Options dialog, OpenOffice.org|Security branch to add a
'Sign...' button to the right of or below 'Open this document in read-only mode'
check box (similar to Protect... button associated with Record changes check box)
o For signed document when mouse is over signature message area add to hover
text 'Saving any changes to this document will remove all signatures.'

The intent is to build the interface so the average user, who won't RTFM and who
probably won't find their way to a support list, would understand easily from
using the application that signing prevents undetected changes to the document.