QuickBooks does not allow for going backward. Once you upgrade to a newer version, you are not able to undo this action and go back to a previous version. When you do upgrade it forces you to be logged in as the administrator and prompts a typed confirmation to be certain you really want to upgrade. A few items can be exported back to a previous version, just not the entire company file.
Using Third-Party Software
Acquire a third-party software program to convert Enterprise back to Pro. There are a few on the market, though such a program may not convert all the data cleanly. Before converting, be sure to create a complete backup file in case there are any problems with the conversion. This allows you to restore your data to the original state.
Print out a set of financial reports, such as the balance sheet and profit and loss statement, to cross-reference against once you convert to the older version.
Use the software per the programmer's instructions.
Print out the same set of financial reports in your new converted file and compare to the reports from the original file. They should match exactly.
Start New File
The best option is to create a new company file using the data from Enterprise. To begin, export all the lists and accounts to QuickBooks Pro.
Pick a start date for your Pro file. Ideally this would be the beginning of a fiscal year, but the start of a month or quarter will work as well.
Reconcile your Enterprise file for the last day of the period. For example, if you are using January 1 as your new start date, reconcile the Enterprise file as of December 31.
Use the closing balances for your reconciled accounts as the new opening balances for the Pro file. Essentially, all accounts that show up on your balance sheet, with the exception of retained earnings, should have an opening balance in your new file. These opening balances will post against opening balance equity.
If you used the beginning of your fiscal year as the start date for your new file, you won't have any problems running reports for the current year. If you used any other date, run a set of reports in the old file as well as the new file to get a complete history.
It's important to understand that it is not possible to go backward in versions. You are able to export vendor and customer lists to an older version, but the company file will not open in an older version. Generally, there is really no reason to convert backward. Enterprise will do everything that Pro does but allows for a larger file size and offers additional features.
Do not neglect to create the complete backup file before converting or upgrading. Save it to a folder you don't regularly use for your QuickBooks file. Label the file clearly with a date.