Marrying a Brazilian in Pakistan

Yes it is possible.

She should have a certificate from brazil about her matrimonial status stating clearly that she is single,

Her identification and adress.. Information on her id verified, in a transcript.

Once she arrives here,
You can marry her, if she is a muslim, christian or a jew.

After that you get a marriage certificate from union council.

This certificate has to be attested by ministry of foreign affairs.

Then you can apply online on NADRA website for obtaining a Pakistan Origin Card.

I hope that answers all.

If they want, Karachi is a town. They can live happily here. It is a quiet town. Its name is Kemari. It was an island. Now it is like an urban population. There is no danger, especially for women. This city and town is very safe. The rest is up to you