Well, the pdf_set_info is used to set info such as the creator, Author name, And the subject of the document.
The Syntax of the pdf_set_info is: pdf_set_info("pdf object", "Author", "The value of the Author").
It's all explaind in the exmable below:
// $pdf is the name of the pdf ducoment you created.
pdf_set_info($pdf, "author", "Ahmed");
pdf_set_info($pdf, "title", "PDF tutorial");
pdf_set_info($pdf, "subject" , "PDF tutorial");
pdf_set_info($pdf, "creator", "php.net");
I wish it works with you ;)