Hi,
I am experiencing the same issue - Since the last windows update PDFCreator fails to switch to the PDFCreator printer and sends printing to the default printer.
I noticed that this issue occurred only on machines with Microsoft Office 2016 using the latest update (1712 Build 8827.2148) and happened when I try to convert xls/xlsx files (it does work for doc/docx files).
I also tried to use PrintFileSwitchingPrinters and failed to fix this issue.
I tried it using PDFCreator V2.1 and V3.1 - both failed to switch the printer.
Can you please assist?