For example, if you are sending the indian passport for TRV stamping. How you send it?? You go to the canada post, and buy two envelopes right, one is called pickup, which illustrates that you are sending the document to CPC ottawa office from your location. And second envelope is used to send your document back to your address, once the process is complete.
So, this is how prepaid envelope works. Moreover this is not a third party courier, this is a registered Purolator company (Purolator is a Canadian courier that is owned by Canada Post (91%)).
Any one can trust it. And No one is providing the docs to any agent, we are buying Purolator labels from an agent simple. There is no "BLS Courier", Bls is partnerships with Purolator, thats it.
Even you can go directly to any Purolator, buy pickup label and return courier label. And send the docs to BLS, and add return courier label along with the envelope. Once the process is complete, you will get your document using the same return courier label that you have sent with the application on the first.
Moreover, if you visit BLS they charge one way courier 70$, 60 for courier and 10$ some random receipt. Yes one way courier, i have to book an appoitnment, skip my work, even after booking the appointment, i need to wait for 3-4 hrs. Once i visit the counter, they find silly mistakes, if they cant able to find, they come to the photo, then courier.
Photo online is 9$, but they charge 18$. I'm not pushing anybody, giving a way, people can buy this value added services in a cheaper way as well, instead of paying high amount than mentioned on the website.
And why people need to pay 40$ for form filling, they can do it on their own, simple mistakes are accepted mostly in Postal, for stupid reasons they cant send back, as they have to mention the mistakes in written, that they cant do it.
They are doing these things only in the walk-in, as they dont need to provide any written proofs.