The "Print" button can be moved or restored through Customize. I don't see a Print Preview button though. You might have to use "Customize Buttons" to get that one.

see item #4 in topic "Fix Firefox 4.0 toolbar user interface, problems (Make Firefox 4.0 look like 3.6) (#fx4interface)" of Firefox Problems & Issues (Notes)

You can generate toolbar buttons for menu and options items using Custom Toolbar Buttons Maker

I would suggest using menu or using keyboard shortcuts rather adding clutter to toolbars.

Firefox and other Browser Keyboard Shortcuts (Comparison Table)

Keyboard shortcuts | How to | Firefox Help

Here's a couple of extensions.

Replace the default "Print" button with the Mozilla Suite "Print/Print Preview" toolbar button/menu, with additional "Page setup" option. Adds Print and Print Preview to the context menu.
https://addons.mozilla.org/en-US/firefox/addon/print-print-preview-update/
This one adds Print and Print Preview context menu items, no change to the default Print button.
https://addons.mozilla.org/en-US/firefox/addon/print-it-146376/

On my version of Firefox 4.0.1, the Print Preview is accessed by clicking on the orange "Firefox" button in the upper-left corner of the window, then hovering my mouse over the "Print..." item in the drop-down (pop-up?) list. This opens another list which includes "Print Preview".

(Alternately, I just now discovered, if I just press the ALT key by itself, then the "old-style" menu bar opens up, and under "File" is "Print Preview". Not really better, IMHO.)

Anyway, I hate it. I use Print Preview ALL the time, and this is more difficult than it should be. I want it to be one step away, but there's no button/icon that can be added to the toolbar, plus there is not keyboard shortcut. I'm very sad and frustrated since I upgraded.  :-(

Firefox has never had a button for Print Preview, only for Print - and that is still in Firefox 4.

Did you try either of the add-ons / extensions that I mentioned?

I'll have to check on my 3.6.? version of ff at home. (I upgraded here at work.)

But my point is that at least the "Print Preview" menu item was on the FIRST drop-down menu under File (or whatever) -- so just 2 clicks away. Now it's 3 clicks away: "orange Firefox 'button'" --> "Print..." --> "Print Preview". Boo, hoo.

I just now tried Print-It! It doesn't seem to be working on my computer.

I also tried Print / Print Preview (Update), and it does seem to work, and eliminates one click.

Thanks the-edmeister!

Wrong. FF has had a print preview button, I've been using it for years. And even with ff5 it is still not available. AND, clocking the ff icon does not show it either!!

You are wrong. FF has had a print preview button, and getting an update to FF should not remove features, it should make them easier to use. This is very troubling, the FF folks do not know what they are doing, now that they have a larger slice of the pie.

We do not want a keyboard shortcut, we want a mouse clickable icon that has been there all along until recently.

I totally concur. We want/need an icon that we can put on the Menu Bar, click it once and have it bring up Print Preview. This add-on does exactly what we need but unfortunately, it's no longer supported.

Firefox has always had a Print button, which is in the Customize Palette - the user has to place it on a toolbar; but Firefox has never had a Print Preview button or access to Print Preview from the Print button. There are extensions available to add a Print Preview button to Firefox, as I mentioned 6 months ago.
https://addons.mozilla.org/en-US/firefox/addon/print-print-preview-update/

https://support.mozilla.com/en-US/kb/How+to+customize+the+toolbar
http://kb.mozillazine.org/Toolbar_customization