If you want to include a file, like a PDF, in your content -- you will select the linking option in the WYSIWYG editor toolbar. Highlight some text to link that directly to your PDF, something like "Download PDF."
Use the "Choose" button to search for a file in your SiteWrench files section. You can browse for a document, upload it to Files, and select it to insert it. Set it to Open in a New Window if you'd like someone to click on your PDF, then have it open in a new browser tab rather than the same browser tab they're currently viewing.