To add a PDF to a page you first need to upload it, please see: How to Upload a PDF File
Now you will need to access the page that you are creating.
Go to: CONTENT >> EDIT WEB PAGES
Click Edit on the page:
You can add the PDF link to text, to an image or both.
Highlight the text area and Click on Insert Link.
Add the path to your PDF:
Add just the relative part of the URL like this: /our_pdfs/cat_in_the_hat.pdf
Click on the image, and follow the same steps.
Click on Save Web Page.
Lastly, Click on View Page: