how to set logo in Pdf First page only

That depends on which kind of logo you would like to add: watermark, logo in header, logo in footer.

With watermark you have not much flexibility – it appears on each page. With headers-footers there are different ways to control it. See:

html-pdf-faq-f1/pdf-page-headers-footers-definition-options-t41.html
html-pdf-faq-f1/is-it-possible-to-set-header-footer-scope-via-the-api-t176.html

Also if you need the image at the bottom part of the first page, <pd4ml:footnote> may also help:

<pd4ml:footnote noref=true><hr><img alt="Image from the forum topic: how to set logo in Pdf First page only" src="..."></pd4ml:footnote>

The info should help:

html-pdf-faq-f1/is-it-possible-to-set-header-footer-scope-via-the-api-t176.html