[Typo3] where to store supportive documents?

[Bing Du]

Some documents do not belong to anywhere in the page tree.  But they 
could be referenced a lot by other pages.  How do people handle these 
supportive documents?  Should they be put in the storage folder or put 
them where as closely as they relate to in the page tree and just make 
them 'not in menu'?

I'd appreciate if anybody would like to share their experience.

Bing