You are correct. There are many websites out there that claim to do this. Almost all of them simply do a slightly better job than cutting & pasting the data off the PDF using reader. This rarely gives you results that will save any time.
The only one I've found that actually works is a product called EDI Link Connect. They too are a website but the difference is that they create a template that matches your PDF so you can convert any non-scanned PDF into a XML or CSV file to match your requirements exactly. So Invoices, Purchase orders, reports can all be converted to the EXACT datafile you need for your purposes. Its also 100% accurate which is extremely important. I've used them a few times for clients of mine who want to eliminate the data entry of various business documents they have.
The site is http://ecdynamics.com/pdf-conversion.php