Should you include PDFs in your optimization strategy for your web site?  The answer is a definite Yes.  PDF are the standard for sharing and displaying documents on the Internet.  The question is:  Can Search Engines find them and optimize them accordingly to a specifc strategy?
 
You have seen and maybe even quite often Search Engine Listings to a PDF that has a non-sensical title and description not related to the content of the PDF.  This is because the Search Engine is trying to make sense of PDF document that is not probably optimized.  Most Search Engines esp Google can index PDFs, but some work is required to get it properly optimized.
 
First off, make sure you actually have text in your PDF not just images.  Next make sure you have a document that is structured with text that follows your SEO objectives for that document.  The "reading order" is the natural way in which the Search Engine sees the text in your document.  The "reading order" can be viewed with a PDF creation and editing tool such as Adobe Acrobat by selecting Advanced>Accessibility>Touch Up Reading Order form the top menu bar.  Use the Touch Up Reading Order feature to change the order in which text gets read or indexed by the engines.  You can also use PDF tagging feature to force engines to read your document based on your tag structure.  Engines also see links in PDFs also think about using PDFs as part of you internal and external linking strategy to increase visibility and authority of your site.