Hello Roy,
Yes, you can print batch of Sales order from Method also. You have to add a Print button in your SalesOrderlist grid and then assign actions to that button to go throgh all the sales order and give you desired result. For that you have to customize your Sales order screen. In order to accomplish that create a copy of the SalesOrder screen by clicking on Customize -> Screens -> QuickBooks_SalesOrder. Once the copy is created click on it to edit it.
Once you are in the edit mode, first thing you can do is add "To be Printed" to your SalesOrderlist grid, you can achieve that by click on Edit on the SalesOrderList grid.
Once you click on edit, a small pop-up window will appear and on step 2 of 9, you can select and add "IsToBePrinted" field to the colum of the grid.
Once the field is added, you can click finish and get back to the edit mode, now from the left pane Click on the Add Object and drag the button object to the Existing Sales Order Grid and call it as Print and then click on edit on the Print Button to assign action to that print Button.
On step 2 of 3: Button Actions, add these actions from the list, in order to check the details of the actions, you can also check the Invoice screen actions on the Print Button they also work the same way.
Once you assign those actions, your Sales order screen would look like the screen below in the screenshot with Print button at the bottom of the grid and "IsToBePrinted" showing in your grid, and once you click on the Print all button it will print all the sales order with checked "TobePrinted" field on your sales order list.
I hope this helps.
-Inder