no, when you purchase car, go to excise office, you will get deed from there, the owner should be present to get deed, when the owner signs and puts thumb impression on deed, he loses his owenership and you get it....
deed can be availed from main GPO normally like here in Pindi ISB, not sure about karachi,
also make sure the file is with owner or not, if the file is with owner, there would be a stamp on the book from excise office that, "original file is returned to owner"
if this stamp is on the book, and owner does not have file, then dont buy it unless you verifiy the file....