This picture is most likely taken during landing. The flaps configuration is the best clue. Flaps are extended more for landing than they are for takeoff. Compare with other pictures of Air Force One:
OP, brightness adjusted:
Landing (original)
Takeoff (source)
The difference in flaps is a bit subtle but seems to match landing best.
Other good clues for cases like this, but that aren't of any help here:
Spoilers or reverse thrust deployed, which will indicate a landing. The angle of the photo is bad for seeing this, and it would be a little early for them anyway.
Smoke from the tires, indicating touchdown on landing. It could be off screen, but it's also hard to tell for sure if the tires are on the ground.
Clues from other scenery in the image that will help place the aircraft at a certain point on the runway. Landings should be near a threshold, takeoffs will be further down. There isn't much to go on in the OP but with a location it may offer clues.
Based on the lighting this picture was clearly taken around mid-day. We can look at the history of recent presidential visits to the Seattle area to see when Air Force One would have been on the runway around that time.
October 2015 - AF1 arrived during the day and left in the evening. If this photo is from 2015 it would have to be a landing. However, those photos show a more hazy/overcast sky while the OP photo looks more clear.
July 2014 - AF1 arrived just after 1500 local and left in the evening again. The shadows seem to suggest that the OP photo was earlier than 1500 local (hangars still in daylight, see 2010 photos) but it would still be more plausible than a departure.
April 2014 - AF1 flew to KPAE.
November 2013 - AF1 flew to KSEA.
February 2012 - AF1 flew to KPAE.
October 2010 - AF1 flew into KBFI, looking for a good reference.
August 2010 - AF1 arrived in the evening, and left during the afternoon. If the OP is from 2010 this would support a departure. But the photo of the departure has different lighting than the OP.