They can send you a letter of invitation but other than the proof of that the wedding is happen (invitation) you don’t need anything. It will be up to you to show that your ties to Pakistan (longterm employment, property if you have any, dependent family members especially children and spouses, etc.), savings to pay for your trip without using most of your savings, international travel to especially US, UK, Australia, other western or Northern European countries, etc. A TRV is mostly dependent on the visitors profile not the person in Canada.