Converting large manuals to web

Microsoft Office Word Docmanagement

We have several large manuals that have traditionaly been printed and 
distibuted in binders. I am trying to figure out the best way to republish 
these for access in our SharePoint site. 

If I save as Web page, I get a huge file with no navigation, which is not 
very good. 

Do I need to split the original DOC file into multiple files, then convert 
to HTML and then manually create navigation or is there some other approach 
that I am missing?
SharePoint can handle these documents in their native format.
This is usually the best practise, or convert them to PDF so any reader 
cannot (easily) make any changes.
Hope this helps