Need advice, how to show content in categories

[motybz]

I want to add in some categories category that called drawings.
For example, if I sell cell phones in the category of iphone 4 will be a sub-category of "drawings of iphone4".
This category will display a number Pdf files.
In addition I want to create a main category named "Drawings" and it will show all the sub-categories of the other categories Drawings
For example, such a structure would be: Cell phones / iPhone / iPhone 4 / iPhone 4's Drawings
And that category will also appear under Drawings / Drawings for iPhone 4.
am i clear?