Method 1: Inbuilt PDF Feature
Dragging and dropping a PDF inside a page allows you to reference it inline, open it on the side, and save its annotations in your page:
You can also do 
Method 2: iframe
If you absolutely need your PDF to display inline inside your page as view-only, use an <iframe> HTML tag like this:
<iframe src="Link-to-PDF-file" width="100%" height="650"></iframe>
Demo of both
