Edit the page where you want to include the link.
Type in the text you want to use as the link (ie, "Download the handbook").
Select that text.
Click the link button in the editor (it looks like a little chainlink).
Click the red/white/blue browse button (to the right of the Link URL box).
The browse window will appear.
Click Choose Files.
Browse on your computer, find the file, double-click on it.
Click Upload to server.
Double-click on the name of the file you uploaded. You can also click the box to the left of the file, then click Insert under the preview box.