Printout of PCB layout


I have done a 4 layer PCB layout in Kicad. It is a plug in board and have plug in headers on bottom side. I wish to check if headers are at right place by taking a print of layout and putting it over the board for which the plug in is made. In that case should I use mirror option when taking print out if my headers are on bottom side?Why do we have to enable mirror when we print top layer.Thanks in advance.

With regards

If you print the bottom from the top (not mirrored) and stick the pins through from the top first to mark them out and then put the connectors/headers on the not-printed side of the paper you can check alignment as well?!

I don’t get this part?: