So I've been using photoshop religiously for about 8 years now, and just this year started getting more heavily involved with indesign and a few differences still confuse me more than they help. I've just run into a problem where I want to add an inch or so to the bottom of my document, but not the top. In photoshop I can say canvas size, and choose an anchor point that the page size is added too. In indesign, I can use the document set up, or in the pages tool I can edit the page size, but no where can I find a way to edit page sized based on an anchor point?
With the page tool you can fix with the proxy in the control bar where from the page is extended or reduced. But I would not recommend to change a page size with that tool except you have to di it with a single page only.
But be aware that an Object Program like AI or ID are way different than Pixel Programs like Photoshop. The method how page elements are used is VERY different.
Normally InDesign uses margins and guides to align with when Layout Adjustment is done. This should be done via Layout Adjustment. The use of such guide lines is very important. Problem is often that people draw their frames without any connection to those guides. That will cause huge problems.
An alternative way is to use Liquid Layout Policy where you have different rules to adjust content when page sizes change.