What versions of OS and OmniWeb are you using? With what I believe to be a stock setup, using 10.6.2 and r125886 (the latest 5.10.2 sneaky peek available at the moment), if I visit a page containing a PDF file, such as the OmniWeb manual at
http://downloads.omnigroup.com/softw...5.0-Manual.pdf and attempt to save the page with File->Save (cmd-S) after loading it, I get a sheet that offers me the choice of saving the file as Source or as a Web Archive, and if I choose Source, double-clicking the resulting file opens it in Preview with no extra steps required. Clicking on the Save button that shows up over the bottom center when the document is first loaded in OmniWeb produces an identical result.
Can you give an example of a page that produces this behavior for you, if it works properly for the URL mentioned above, but not for others?
By the way, searches on the forum for 3-letter strings don't ever return any results in my experience. So, searching for "PDFs" will get a bunch of hits, but not "PDF" -- kind of a bummer when you can't be sure that the post you want to find had a 4-letter string you can identify!