AutoCAD 2010 :: How To Merge Lines

As more and more clients, subs, etc., etc are requesting pdf's more and more often, the issue of "lines merge" vs. "lines overwrite" (and therefore, pdf "flattening" when printing a pdf) is becoming more of a topic of discussion in our office.

I know we're not the only office making pdf's that have to be "flattened" (thereby taking a huge amount more of time to print) when sending to a printer.... but not *all* pdf's we receive need to be flattened so there are some offices that don't have to deal with this issue.

The question is this:

If you use lines merge = on in your autocad, do you have a way to get pdfs that don't need to be flattened? (printing to dwf then pdf is not a reliable option either, as that does not consistantly honor the lines merge feature between dwf/pdf either)

If you don't use lines merge then how do you set up your drawings to allow for easy draworder handling? (and do you use solid hatching patterns in your drawings, which we rely on alot)