The website I am working on has a few hundred PDFs in it.  I don't think I have ever seen any of them come back in a search but there are linked to directly from out site.  They are also full of keywords because they are product documents.Is there anything special we need to do to get Google or other search engines to crawl them?Is there any hard and fast rules for making PDFs to help Google like them more?  For instance should I run them through ghostscript to clean up broken PDF tags that Adobe creates during generation?
Do search engines crawl PDFs and if so are there any rules to follow when making them
seo;pdf
Google definitely indexes PDF files and you can search just for PDF files by adding filetype:pdf to your search query (example).I would say the main things to do to optimise a PDF so it's easily indexed would be:Give it a meaningful filenameComplete all the document metadata properties (title, author, keywords etc)Make sure your PDF is comprised of actual text and not scanned imagesEnsure you have good content with correct use of headings, just as you would an HTML documentFor more tips read Optimizing PDF Documents and Eleven Tips For Optimizing PDFs For Search Engines