Personally, I find physician assisted suicide morally wrong, so my arguments would probably be similar to those found in the paper you read. But I can think of a few points people who support physician assisted suicide might use to argue their side.
1. "It's a choice." People who support abortion also use this statement to support their opinions. This argument probably has more validity than any of the others that could be raised during a debate about physician assisted suicide, because it's true. A person does have the right to make choices about their own life, including whether or not they want to live it. However, this argument is even trickier to debate when talking about physician assisted suicide than it is when discussing abortion, because the person whose life will end is deliberately making the choice to do so. (As opposed to abortion, when a mother or father chooses to terminate the pregnancy- the fetus obviously can't choose this.)
A question you could develop from this standpoint might go along the lines of "Do you think physician assisted suicide is a valid choice?" If people say yes (some will), then ask "What makes it different than suicide that is not administered by a doctor?" (Is it okay to kill yourself for other reasons or through other methods? Why or why not?)
2. "They're in a lot of pain." This one kind of goes along with the choice argument. The people who choose physician assisted suicide are almost always suffering from a terminal, painful illness and don't want to prolong their suffering. This argument is also hard to debate, because saying that a sick person "might get better" is a little insensitive. We can't understand another person's pain, especially when the person/people in question are suffering from an extensive, terrible disease.
A question you could ask from this argument could go something like "Some people think of committing suicide as giving up. If a person is legitimately in pain and will eventually die from their illness, is their choice to be euthanized really giving up?" People will have strong reactions to this question, because it's so controversial. Some will say it is giving up, because you should "fight until you die" and hold on to hope for a cure or recovery. Others will argue that suicide is a way out, of getting rid of the pain and dying peacefully.
3. "It's their (physician's) job to help others." The last argument I can think of. There is some truth to this, as with the other arguments above. Doctors work to heal others, to make their pain go away. In some cases, there is no medicine, therapy, or surgery that will restore a patient to health. Many people say that the most "humane" thing to do in a "hopeless" situation like this is to make the pain go away altogether through death. In this scenario, the doctors are like heroes, because they help change a suffering person's life (by ending it).
A question you could ask about this topic would be "What do you think of the role of the physician in these suicides? Are they "killers" because they are ending a life, or are they "heroes" because they are helping a person find comfort?"
These are the main standpoints I can think of that differ from the Catholic perspective. I want you to know that even though I don't agree with any of them, I can see why someone would see them as valid arguments for supporting physician assisted suicide.
Good luck with your discussion! Since it sounds like you're the moderator, be sure to raise questions in an unbiased way and listen to every person who answers. If some people aren't participating, you could casually put your next question to them so that they feel like their opinions will be valued within the group. Also (and I'm sure you know this), don't put down other people's opinions. This is a discussion, not a debate (I'm assuming) so don't try to tell others why they are "wrong." I got the impression that you are Catholic from the description of the paper you read, so remember to pray for guidance and inspiration beforehand, and good luck!