Although it is possible to number pages this way in Word, I would not
attempt this type of project in a single document unless each page's content
is to be self-contained. If you want the instructor notes to flow from their
page 1 to their page 2 and the training materials to do the same, then it
will be much simpler to create two separate documents and collate them
manually.

If you insist on numbering the pages this way, you will need to select
"Different odd and even" header/footer so that you can have different page
numbers on the recto and verso pages. The following assumes that you want
the matching pages to be facing pages (you will need to skip the actual page
1). For the recto (right-hand, basically odd) pages, use this field:

{ = ( { PAGE }-1)/2 }

For the verso (left-hand, basically even) pages, use this field:

{ = { PAGE }/2 }