I am not saying he does not have a good reason for divorce, I am saying that as healthy as he may look by comparison, he picked sick.
If you want to be extra kind and you have the phone number of a counsellor/religious leader to refer them to, great, hand it over and walk away. Do not engage. If these were the kind of people who did have boundaries, it would be great to try to support them. That is not the case here.
These are excellent points.
It's important to keep in mind that it's really hard to get a true picture of what is going on inside a marriage, and often it's a lot more complicated than it appears on the surface. I've known a few guys who were married to really needy, not very stable, high drama women. In every case, the guy married her with lot of experience of what she was like, but chose it anyways (I think there was often a white knight, saving the poor girl impulse involved, which suffered when they realized that no, she wasn't going to change). I've also known people who looked like perfect gentlemen/ladies in public, and were significantly different in private.
At the same time, that doesn't mean you should cut loose divorcing friends completely, because a healthy network of friends and family can make a big difference as someone struggles through a divorce and rebuilds their life, from either side of the situation. When someone is divorcing, there is a tendency for friends to avoid them, because they don't feel comfortable, leaving them isolated when they do need support.
I agree with PPs that keeping far away from Annie is a very, very wise move. Don't answer her phone calls - delete messages unheard. Don't answer emails. If she does get through to you, say "I don't want to be involved" or even "I'm really busy right now". From what you've said, Annie isn't your friend - she's the soon to be ex-wife of a coworker you are friendly with, and someone you actively dislike and have never wanted to spend time with. I also agree with PPs that she is likely looking for someone new to latch on to for panic phone calls and help navigating the basics of life. You don't want to be that person.
For Paul, it's a bit different. It sounds like you to want offer friendly support without getting dragged into the dirt with him. He's a long-time work colleague you are friendly with, rather than a good friend, so your support should match that.
So you can support him in a healthy way. Chat with him about non-divorce related thing at coffee breaks or lunch - friendly social contact can be a big help to someone going through a divorce. Pass him information to resources that can can use for help if it is appropriate - support groups, counselling, etc.
What you don't want to do is get dragged into listening to him bad-mouth his wife. If he starts with that, you can cut him off, with a "That's more than I want to know", leaving if necessary. If he keeps away from the topic, then you can keep up the office-friendly interaction.