Folk have struggled with WORD and extra pages for decades. Time and time again it's a blank page that shows with I view the document in Word.
As to why documents change when the printer changes, that's how Windows works.
If you want to lock down a document, try making a PDF next time.
Wife's company added a new Epson FX890II to replace a broken FX890 (notice the missing II). They are using Windows XP believe it or not.
Nothing has changed beyond installing the drivers and it prints the documents from their software just fine except it ejects an extra blank page after printing is done. This did not happen with the old printer.