1
In the Print dialog, ensure your physical printer is set as the default printer to use, not a virtual pdf printer.
2
If you still see the save file dialog when you try to print a document, save the file, then check the file that is saved, is it a .prn file type that is saved?
If so.
Close all open Applications
In the Settings App, go to Bluetooth and Devices - Printers and Scanners
Select your printer and choose 'Printer Properties'
On the resulting dialog, choose the Ports tab
Is the Port set to Print to File?
If so, change that to LPT1 (if your printer is connected by USB) or WSD (if your printer is wireless) and save that setting
Then try printing again.