What are cost-effective, reliable ways to receive online payments in Pakistan?

Having followed the payments space in Pakistan for over 15+ years, I can comment on your answer.

• On Paypal acceptance. You cannot (legally).
• Since PayPal is not offered in Pakistan, you cannot accept it.
• You can however, utilize the PayPal of your friend, relative or even 3rd party providers. However, the caveats are stacked against you. PayPal account get unilaterally blocked (if PayPal sees that it is being used as an aggregator for payments. Their software is very good at detecting this). Though this option is available to you, it is not recommended. Short-run it might work, long term, guaranteed to go against you.
• PayPal accounts that you use in proxy, would result in extra income for the person whose PayPal account you are using, and can have additional taxes imposed or tax related questions during audit.
• If you use providers like https://moneyinpakistan.com/home... - be sure to notice, they do not carry an MSB (Money Service Business) licence, and are not legally licensed to do the transactions they are doing, since they are an aggregator. The company is also not registered with PRI (Pakistan Remittance Initiative) nor with SBP as an incoming tie-up for foreign-currency. They are not doing any SAR, OFAC, CTR, AML, KYC checks. Get caught with them when they go down (and they will go down sooner than later) and you can find yourself on the wrong side of the fence, when it comes to the law. Last I heard, they were reported to FinCEN and are being investigated (companies and people who operate such companies, give Pakistan a bad name).
• So, long story short, PayPal is out.
• Your options to receive payments are plenty. Almost every other legal channel through which payments can be received are open to you. From Western Union, Moneygram, Xoom, SWIFT Wire Transfer, Credit Card acceptance, and even pre-loaded Visa/Mastercards. The right question to ask is what is your customer will to use as a financial instrument for payment to you!
• As a person, you are freely allowed to operate a foreign currency account in Pakistan. This can be in USD, GBP, Euro, etc.
• Companies like 2Checkout (see http://www.2checkout.com) are the best. 1000s of Pakistani freelancers and small and medium vendors use it. They have an excellent track record. Also, if digital goods is your domain, check out Plimus (http://www.plimus.com). Other alternatives are AlertPay, Payoneer, and countless others. You just have to do a bit of research and their are literally 1000s of companies who will provide 3rd party merchant services to you.