The joy of your short time request is that it's entirely possible to use conventional storage methods. In this case rather than having to carve it into granite or similar as per the Rosetta Stone, we can actually write it long form on parchment.
While occasional documents dating back to the 6thC show up in good condition, far older documents have been found in admittedly not great condition but also without any apparent attempt at preservation. In more modern usage, the British Parliamentary archive has vast quantities of scrolls dating back up to 500 years.
All sorts of grand ideas about electronic storage are likely to be considered, but given that most people can't read removable media from only 15 years ago, the chances of anything electronic being readable in a thousand years are pretty much nil. So whether you choose to carve it on granite slabs 3m high or write on parchment scrolls 10m long, you need to write it out longhand.