The most prominent example of "pride" in Jane Austen's novel, Pride and Prejudice are Elizabeth's behavior with Darcy, and with her family.
Although Darcy acts foolishly towards Elizabeth and her family at the beginning of the novel, looking down on them because of their "social inferiority" and country manners, he is a man who is able to revisit decisions he makes and change his mind if he believes he has been wrong in his judgment. However, Elizabeth, who believes herself perhaps ethically superior to Darcy is unable to recognize that perhaps she doesn't know him as well as she thinks; nor does she revisit her feelings towards him until the proof is right there in front of her, irrefutable—that he is not the devil she imagines him to be. It seems that Darcy is able to change his preconceptions based on what he witnesses with regard to Elizabeth and her family, despite what others may say. Elizabeth cannot see the good in Darcy, perhaps letting her overblown sense of pride with Darcy blind her to what is right before her eyes.
However, Elizabeth's pride is also a positive thing in how she protects her family and herself. When she overhears Darcy making a rude comment about why he won't dance with Elizabeth, she refuses to let the comment make her feel small. She takes pride in who she is, and regardless of social standing, knows that she has value that has nothing to do with the opinions of others.
Though her family sometimes embarrasses her with their "rough" country ways, she still has a sense of pride in them. They are good people; they love and support each other; and, they are generally patient with Elizabeth's feistiness.
In the novel, there are two sides to pride. On one hand, it interferes with the way Elizabeth sees Darcy, and her refusal to give him the benefit of the doubt.
By trusting entirely to her own observations (pride)..., Elizabeth threatens her future happiness with Fitzwilliam Darcy.
However, in defending her family from the nasty behavior of people like the Bingley women, Elizabeth demonstrates a sense of pride in who she is and the family from which she comes.