Monthly backup of SQL server DB to PostgreSQL?
Can you not just hook Crystal Reports to an instance of MS SQL Server? That way the process should be as simple as "backup the live database, restore it into test/snapshot location when needed".

If the database is less than 10Gb in size you can use SQL Express so there would be no licensing implications, if it is 10Gb or more than you could restore it on the same SQL Server under a different name assuming you have access to be able to do that. Otherwise you might end up paying for an instance of SQL Server (avoiding this may be why you are using postgres in the first place).

If you have a specific process that you are currently following manually which you would like to automate, then you need to specify that process in detail in your question otherwise we can only guess and that may not be helpful.