This is what they do in the UK. Firstly, they want to remove your contact details, so that the company can't get in touch with you directly. So they replace your header with theirs. Secondly, there's a list of things that hiring processes can't discriminate against, legally, so the recruitment consultants remove things such as age, nationality and marital status. Thirdly, and here we're on shaky ground, they might tweak it to make relevant skills for the position stand out. Finally, disreputable recruiters will flat out lie on your CV when passing it on.