As long as the PDF is rastorized (flattened) to an image and the text is embedded, it's pretty much a cinch.
There are a few caveats though. If you save out a PDF and apply security preferences to it, the contents are encrypted and can't be read by the Search Engines.
If it doesn't matter that the end user can copy text or print the page, don't lock it up.
Here are a couple of articles of interest:
SEO Your PDF's - Does This Work?
Optimizing PDFs for SEO
Good Luck!