trust me bhai jaan if PAF "really WANTS " Su35 and is ready to pay for it in cash there is no reason why russia would say no but there are three problems
1. your pilots have endurence level of couple of hours in fighter jets deu to single engine and medium feul requirement while twin engine heavies with big feul tank like flankers have endurence of 3-5"su27" hours going upto 6-8"su-35" and pilots have to start training on that level and all that takes loads of money and time and will take at least a decade to make a nee doctroine based around them even if you order them tommorow ... ask
@MastanKhan or
@gambit about it
2.mantainence of russian fighter jets is at least 2X times more as compared to american or french fighters which becomes twice when its a twin engine meaning a su35 would approx nead at least 4 times more mantainence time than a F16
3.cost or weapons and allied systems apart from fly away +mantinence and training dont forget you have to buy complete set of weapons package and allied products like tooling and engine aids and PODS which all costs money
all in all aif PAF decides to buy say 54 Su35 with spares and training and maintainece aides /pakage and weapons pakage it will still cost around 150 millon as you have to install a whole infra for it