Generally if a constituent document such as a discretionary or SMSF trust deed is lost you would need to do a deed of lost deed. On that it is a good idea to go to all your clients and ensure they all have copies of their deeds. A lost deed can create significant problems in divorce, death and even getting a bank loan.
However for companies, section 137 of the Corporations Act 2001 allows the shareholders to update a company constitution with a simple resolution. This is a good idea anyway as our constitution enables the use of the Successor Director. To upgrade go here: https://www.lightyeardocs.com.au/product/upgrade-to-lightyear-docs-standard-company