Mine is doing this already, but I think I know how to check yours. See the screenshots for more info. First, I have the Reader app (from Microsoft, not Adobe) installed. I think it came pre-installed. I have a PDF in My Documents that contains "Auxiliary Equipment," and if I search for that text by going to the Search charm, typing that in, and tapping Files, my PDF is shown in the results. To check your Indexing settings, go to the Search charm and type "indexing options" and then tap Settings. Tap on the "Indexing Options" search result. This will take you to the Desktop. On the Indexing Options window, I clicked Users in the Included Locations list, and then the Advanced button. On the Advanced Options dialog window that opened, I scrolled down in the list on the File Types tab until I found "pdf". Mine was already checked. Notice in the screenshot it says "Reader Search Handler" next to it. Click the list item to highlight it, and make sure "Index Properties and File Contents" is selected in the options below. Click OK and then close the Indexing Options window. Screenshots:
Searching for text in PDF
PDF in Reader app showing the text
Search for Indexing Options
Indexing Options on the Desktop