Need Help here

In your existing code, you're working with an object named $pdf. I assume this depends on a third-party library.
You can use this in CI as well.
E.g. the fpdf library. The Fpdf.php file goes into the application/libraries folder. In CI 3.x it must have a first capital letter.

In my controller where I want to generate a pdf, I have this code:

PHP Code:

$this->load->library('fpdf'); 


This creates an object.
The methods and properties of this object are addressed like this:

PHP Code:

$this->fpdf->AddPage('L');
$this->fpdf->SetFont('Helvetica','',11);
..
..
$this->fpdf->Output("mydocument.pdf","D"); 


Etc.