We need to keep access for the financial data for the next 5 years for a seized company. They use odoo11EE, but can't keep paying licenses. 

What is the best solution to have access?

• to downgrade to 10CE. ( if possible, How?)
• to downgrade to 11CE ( not sure if invoicing will be enough) 
• to export to excel. (will be too complicated. )
• to print our hard copies ( no way)
• to get free odoo one app for Accounting. (does it work?)

Any solution will be appreciated.