I found 2 places in Microsoft Word Home edition 2010 to address this problem and I believe they have both been mentioned here, but here they both are.
1: Select the page layout tab, find page setup (I found it in the Margins, Orientation section) at the bottom of that section, click the box next to page setup and click on the Paper tab. For my Epson XP-960 I selected Cassette-2 for the paper source in the First page and Other pages windows.
2: Select the File tab and select print. When the print options come up at the very bottom is Page Setup. Select that and click on the Paper tab. For my Epson XP-960 I selected Cassette-2 for the paper source in the First page and Other pages windows. The weird thing here is that changing the paper source in the Printer Properties menu does not fix the problem, you must go through the Page Setup menu to correct the problem.
I found that after performing the first solution and then saving the document it retained the setting the next time I opened it. I am not sure if that is true of the second solution.
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