Rather than adding a link to a PDF, you can embed a PDF with a viewer directly into your page. You can upload your PDF before or during this process. The first screen shows the PDF already in the Media Library. 

1) Click the "Add Media" at the top of the page; this opens the Media Library interface.

2) Select your PDF and click the "Insert into page" blue button in bottom right corner.

You will see code with the words PDF embedder included. Do not edit the code within the brackets. When you are finished editing the page, hit publish (for new pages) or update.

On the public side of your webpage, you will see the embedded PDF viewer which has zoom and download options.