PACT teaches that the real issue here is not changing your partner. It's changing how your partner is WITH YOU. How your partner treats you (and vice-versa). If my partner is a shy, introverted type, I am not going to change that. Introversion is one of the most stable personality traits researched. So even if I wanted to change that, even if my partner wanted to change that about him/herself, it's not likely to happen. But if part of how I get my emotional needs met is to have friends over every few weeks my introverted, shy partner may need to learn how to support that for me to some degree. This does not mean that s/he necessarily enjoys these social situations. But s/he does learn to support this need I have to connect with others by inviting them over every so often. Likewise if I am a strongly extroverted person my partner is not going to change that about me. But s/he can expect that I am going to not bowl him/her over with my need to have people at the house every day of the week. S/He can expect that I will allow him/her some "alone time" to recharge at the end of a day where s/he has had to talk to a lot of people. And that I won't take that personally or shame him/her about it.
In this scenario no one is actually changing. I am still an extrovert. He or she is still an introvert. But we respect each other's needs enough to BEHAVE in ways that take care of each other. And yes, you can "ask" for this. I would argue if you don't ask for it you may not get it. And if your partner is not acting in ways that support your deepest needs then they are not doing their job and you are not getting the benefit of being partnered. And over time, this lack of support for your deepest needs may begin to erode the positive feelings towards your partner. The relationship will no longer feel like a place where you can get important needs met.
Where many of us go wrong is in confusing how we want our partner to ACT and who they ARE. We feel disappointed that our partner is not a certain way and forget that we can ask for behaviors that feel good to us, and that our partner can behave in those ways even if it's not their personal default. Of course we need to learn to ask in ways that are respectful and kind and still honor our partner's own needs and wiring.
For an excellent in-depth explanation of how your partner is wired and what is likely to come naturally to them (or not!) see Dr. Stan Tatkin's audio program Your Brain on Love or his bookWired for Love. Or for those of you who are not yet partnered see Dr. Tatkin's book Wired for Dating. Learning how your partner's brain is set up will help you appreciate why they do what they do (and don't do), how to ask for what you want and need and how to take excellent care of them in return.
Wishing you health and happiness in all of your connections,