The PDF documents on your website are probably a mish-mash, provided possibly by different creators and almost certainly at different times. There’s no guarantee they were produced with care, using a PDF creator which wrote the content in such a way that it could be easily extracted. Indeed, I’ve seen PDF datasheets which are actually photographic scans of original documents. Ouch. Those can’t be read by Google at all. One neat trick to finding out what Google sees in a PDF document is to import it into “Google Docs”. If you don’t know about Google Docs, think of it as an online version of Microsoft Office and the like. Some people (including yours truly) now use it for almost everything they do. If you’ve got a Google Account (for e.g GMail, Google Analytics etc) then you’ve already got access to Google Docs. Otherwise, it’s time to create a Google Account.
All you then need to do is to upload your PDF file into Google Docs. Before you click “Start Upload”, ensure you’ve ticked “Convert text from PDF or image files to Google Docs documents.” When Google has finished uploading the document, you’ll see each page presented firstly as an image of the page, and then underneath as a version with all the text extracted …as well as Google can extract it. What I then do is to “Select All” the contents of the document, and paste it into a text editor like Notepad. This gives you an uncluttered view of what Google sees in your PDF document. With any luck, it will be a perfect plain copy of the contents. More likely, it’ll be a lot messier. And that’s why the document isn’t taking the Google results by storm, and could do with being re-created, or at least having an abstract page added.