Capture & Print lets you print an area on a webpage easily. All you need to do is highlight an area and you are ready to go. There is no real simpler way to put this.
Here is a little more about Capture & Print from the developers:
There are several Add-Ons which allows you to capture a webpage’s area, however its primary goal is to save the captured area as an image on your hard-disk. This add-on let’s you forward the captured area directly to your printer, thus saving time if what you want is to print captured areas since no need to load and then print the saved image on disk.
On install, a toolbar button will be added to your browser (which you can customize) There’s also a item on the right-click context-menu. Use any of them to activate the capturing process. You know, click and drag to select the area to capture – then, as soon you leave the mouse button it’ll be automatically sent to the Firefox’s Print Preview window.
Want to see more? You can download this extension from the Firefox Add-ons website.