History with reports

If you want to save each time a document when you click on a report you have only to enter the folowing int the xml-report definition:

'myname' + time.strftime('%Y-%m-%d %H:%M:%S') or direct:
(object.state in ('open','paid')) and ('INV'+(object.number or '').replace('/','') + ' ' + time.strftime('%Y-%m-%d %H:%M:%S'))

So each time when you click on the save button it appends a new docuemen with the time and date in the name.