You can apply for a Pakistan visa on arrival in two ways:
1-If you are a new applicant then you may apply for a new visa if you don’t have a visa.
2-Secondly, if you have a visa and you want to extend your stay then you can apply for a Pakistan visa on arrival.
While applying for a visa online you have required documents:
1-A latest colored photograph
2-A Valid Passport with 2 blank pages for stamping.
3-Invitation letter of the tour operator.