The problem we're solving here is that few end users realize you can run Google-like searches in a PDF you've sent them, even from Reader. The Search command is buried in the Edit menu, while its weaker cousin, Find, gets its own field in the default toolbar, along with the well-known Command/Ctrl-F command.

You can force the Search feature's interactive panel to open by default whenever the PDF is opened, making it QUITE OBVIOUS that the PDF is searchable. It works even if the PDF is opened in the browser window … well, in Safari, at least.

Download this quickie demo PDF I made (just one page) to see it in action:
http://senecadesign.com/demo/search_panel_demo.pdf

To reveal the Search panel automatically in a PDF, open it in Acrobat 8 or 9 and follow these steps:

1. Open the Pages panel in Acrobat (click the Pages icon in the left toolbar, or choose View > Navigation Toolbars > Pages) to view the automatically-generated page thumbnails of the PDF file.
2. Right-click on the Page 1 thumbnail and choose Page Properties from the contextual menu. 
   
3. Click the Actions tab in the Page Properties dialog box. The Select Trigger menu should be at Page Open by default, and the Select Action menu is set to Execute a Menu Item by default. Perfect.
4. Click the Add button to see a list of Menu Items you can specify.
5. Select the menu item "Edit > Search" in the list and click OK.
6. Click OK one more time to save the Page Action and close the Page Properties dialog box, and then save your changes to the PDF.

To test it, close the PDF and then open it again from File > Open Recent. You should see the Search panel immediately appear on the left. Try opening it in Reader, you'll see the same thing.

There are all sorts of fun Page Actions you can add to a given page, you should play around with it when you get a chance. 

The key here though is that by adding a Page Action to the first page of the PDF, and making sure the PDF is set to open to that page — it is by default — in File > Document Properties: Initial View, you can make things happen as soon as a PDF is opened.