Uploading and linking to a pdf file is similar to adding a hyperlink.

1. Highlight the word or phrase you wish to hyperlink.
2. Click the "Link" button in the editor (it looks like the earth with a chain on top of it, shown below)
   
3. On the “Link Info” tab of the popup window, switch the Link Type to URL, and click the “Browse Server” button to open the web-server’s file manager (see screenshot below).
   
4. In the file-manager popup window, click “Upload” from the top left of the toolbar as shown below.
   
5. A small popup will appear in the top left.  Click "Choose File" to choose the PDF from your computer
6. Click the big "Upload" button beneath where you just chose the file
7. Once the upload completes, the file list will refresh.  Close the upload popup at left.  Then select/highlight your file.   A preview of it should appear across the bottom pane.
8. Click "Insert File", which is a few buttons to the right of where you clicked "Upload" (shown below)
   
9. To set the link to open in a new window/tab, click the “Target” tab and change the setting to New Window (_blank) (shown below).
   
10. Click OK