pg_dump from 9.2 to 8.4
First my recommendation is to start with text dumps and expect you may need to manually edit them.  There are a large number of differences between 9.2 and 8.4 and these are especially important if you have used extensions in 9.2.

There are however a few things you can do to make the import less troublesome but slower:


Don't use -F to select a format.  Work with plain text dumps since you can edit them if you need to.
Don't use -j.  Keep things simple.
Use --inserts, so INSERT statements are used instead of copy.


Be prepared to edit the dump if needed.  Be comfortable with text editors used for managing large files (vim or emacs, both of which have Windows versions).