[troyb]

You can get OmniWeb to display PDF files without any helper plug-ins by turning a hidden preference off.

Quit OmniWeb, open a terminal window and enter this:

defaults write com.omnigroup.OmniWeb5 WebKitOmitPDFSupport -bool false

Now restart OmniWeb and PDFs should be displayed in the browser window! This feature is lacking some functionality at the moment but you shouldn't have any problem opening PDFs.