Printer selected from within the AxAcroPDFLib.AxAcroPDF toolbar resets to the default printer

I am developing an VB.Net application (.Net 4.0 framework) in Visual Studio 2013.  I have a control that includes an instance of the AxAcroPDFLib.AxAcroPDF control (named pdfViewer in the user control) from Adobe Reader XI.  This app can have between 2 to 8 instances of the user control, so there can be multiple instances of the AxAcroPDF control.  I'm having no problems loading files into each instance of the control.  The problem I am having is that when the user selects the Print option from the toolbar at the bottom, the printer selected is only retained for a yet-to-be-determined number of minutes, then it seems to reset back to the Default printer.  What could be causing this?  The only method I am invoking is the LoadFile(), once to load with a genuine file to view, and once with a "BLANKPDF" value to get the control to clear itself out.  Any ideas?