pdfpreview
This should be dead simple: how to customize the font including face, style and modifications. But those configurations are nowhere to be seen.
So … where is this hidden Preview/pdf toolbar / icon, whatever that allows setting the font ?
Here is what I see on the menu.
Right clicking on the textbox itself brings up the following – note that no way to change any text font/size. This is absurd.
It does work in Lion, the way you tried it.
In Snow-Leopard you have to select the text itself to change the font(size) by first clicking/selecting the text-field to get the selection rectangle (for re-sizing or moving - as you described) and then click a second time on your text to select all the characters. Now your text should be selected (visible by the highlighting) and you will be able to change the font-size in the Text Properties field.
Edit 2012-01-04:
I could reproduce the problem described and also found a simple solution. If you open your pdf and re-arrange pages or rotate them and then try to change the formating of existing text fields it (sometimes) fails.
The solution/fix is to click the window (menu-)bar of the "Fonts" window, then click on your text field again and finally chose the new font variant → and it will be applied :D
Sadly, it is not possible to change the font used by Preview for Notes - this is denoted by Apple an 'UnEditable'.
This thread on the Apple forums (which I can't take credit for) provides a couple of work arounds such as using Annotations instead of notes (as these are editable) or post-editing comments in Adobe Acrobat Reader XI, but not an actual solution to this problem.
Best Answer
On my Preview in Mavericks it is right below the main menu bar, where I can select the Font and the size.