The key thing here is to remember that a view controller's main view in a nib (.xib file or storyboard) is always resized anyway when it is put into the interface. The size you see it at in the nib editor (Interface Builder) is just a "serving suggestion". Thus, SamirChen's answer is quite right: set the view to Freeform so you can resize, and just make it big enough to hold the scroll view which itself is big enough so that you can put in all the desired contents.
I would add just two points that you will find helpful:
Use autolayout outside the scroll view. This will cause the scroll view to become the right size when the view is resized to fit the interface, and will cause everything else to be repositioned correctly.
Use autolayout inside the scroll view too! This is the really cool part. If you set up sufficient constraints between all the contents of the scroll view and the scroll view itself (their superview), the contentSize
will be calculated for you automatically using constraints from the inside out! Thus, you don't have to know the content size or set it in code!
It is easier to see than to describe, so download the example code from my book and look at the examples currently entitled "bk2ch07p367scrollViewInNibAutolayout" and "bk2ch07p367scrollViewInNibAutolayout2".