Phrasal verbs difference

I can look through the window, but not through the wall.  If the wall is not too high, I can look over it.  That example is easy to understand. 

However, what if I am looking at something like a document or a photo album?  Then, we have some additional meanings.  Now, over has a meaning more like oversee.  If I look through your document, I will likely get a good idea of what is included.  If I look over it, I will additionally draw some conclusions about the work.  You can expect more constructive feedback on it, as well.  If you were submitting reports at work, you might ask a coworker to look through it.  He might tell you that you do or do not have all the parts you need.  Then you give the reports to your boss.  He looks over them in more detail, and will notice if some of the figures are not correct. 

It is a subtle difference.