1-0 is not a good result if you hope to qualify. If you think Dortmund will not get a good result against PSG before the match, I think you are not doing anything good with your mind in analyzing the match.
Dortmund here could be different from in the Champions League. Since the group stage, Dortmund has performed well. Dortmund were even able to advance to the semi-finals through group F, which was called the hell group, and they managed to win the group.
A draw is not safe for Dortmund but 1-0 is an asset when playing in Paris.
It's true that 1-0 winning margin isn't good enough to give them enough confidence in the fact that they can qualify for the finals , but this can be seen as a little edge, although similarly PSG had same encounter at the quarter finals with Barcelona and then it was a goal difference margin and they were actually able to still win Barcelona to qualify for the semifinals when they played at their home.
PSG is usually known for trying to get that extra points especially in games as this, they have always have this champions league dreams and hers it is looking like a rare opportunity for them,they have always tried to make their home a stronghold for their victory and so I'm very optimistic it's going to be as difficult as it was for them in playing in Dortmund home tonight because both team are definitely not going to get it to be easy for the other as they are both wanting to getting the best off this opportunity before them. PSG will do everything possible to have their selves in the champions league finals this season.
Dortmund seeing this is the only opportunity for them to be able to get a trophy this season will try to do everything possible but they sure know it's not going to be easy, interestingly if they get to make it to the finals only to meet Bayern Munich, i think it will be the first time two German teams are having to face each other in the final more like an extension of a bundesliga teams playing a final.