While going through an article on AFO, I came across this little piece of info:
So, does it have retractable steps on all its exit doors? How does it manage doors like these?
There is page by cryptome with documentation about AF1 rescue options.
According to the "TECHNICAL ORDER 00-105E-9, 1 FEBRUARY 2006, REVISION 11." (15 April 2006), slide 71 "AIRSTAIR OPERATION VC-25A", Boeing VC-25 has only two exits equipped with own airstairs, only at doors from lower compartments. Doors at main deck have no integrated airstairs.
First photo in the question shows forward airstairs operation, and there is photo of aft airstairs, used in 2006.
According to this slide from the same PDF, there are 5 pairs of entry doors on main deck by design of the Boeing 747-200 plane; but 3 or them (1R, 3L, 3R) are blocked on VC-25 and can't be used. All doors from main deck have no own retractable stairs.
Also, from here:
Unlike a normal 747, the plane has its own retractable stairways, for the rear entrance and the front entrance. These stairways open onto the lower deck, and crew members and staff climb internal staircases to get to the upper decks.
It doesn't have retractable stairs on every door; the second picture shows mobile stairs to the upper exit (you can see the driver's cabin behind the crowd).
If mobile stairs aren't available the president will descend to the lower level and use the built in stairs at the lower exit as shown in the first picture. If they are available (and deemed to be safe by the bodyguards) they will be used.