While we can tell you the procedure here in Brazil to invite a Pakistani citizen to Brazil, the process in your country may be vastly different. You really need to contact the Pakistani immigrations authorities to inquire directly with them how to proceed.
Generally speaking, you are going to need to provide a notarized Letter of Invitation which gives all of your personal information, address, etc., and also states the full details of the "invitee".
You will probably also need to declare that you accept the full financial responsibility for your "invitee" for the duration of the visit, which will include lodging. You will likely be required to produce financial records to prove that you have the ability to support your invitee. Also you will also need to state that you accept the legal responsibility for insuring that the "invitee" will, in fact, leave Pakistan when the visa stay expires..
Most nations impose these civil obligations upon a sponsor, and there are both civil and criminal consequences for false or omitted information, or failing to insure the individual leaves the country when scheduled to do so.
Cheers,
James   Expat-blog Experts Team