Go to the page you want to add a PDF to. Click the green EDIT PAGE button at top right of page to bring up WYSIWYG editor.

Highlight the text you want to use as your link to this PDF  (or click on the image).

Click the INSERT DOC icon in the WYSIWYG editor toolbar.

Drag your file into that media popup window or click the UPLOAD tab at top left of media popup box, which will then allow you to click the SELECT button to browse for the file on your computer.

Once the file has been uploaded, click the file you just uploaded and click the Insert button at the bottom right of popup box.

Watch the video below to see this in action: