Originally Posted by Sweetpea
The PDFInfo is inside the PDF file. It's called PDFInfo in LaTeX... you can see that data when you look at the properties of the PDF file.
In that case, assuming it's just the normal internally stored pdf metadata, it should work. You need to have the option in Prefs|Import/Export|Add to "read metadata from file contents" turned on. Some pdf files cause problems for the code library used by Calibre to handle pdfs and, as a result, some people have turned off the pdf metadata reader. If you've done that, turn it back on, per Kovid's comment.
edit: You should also be aware that Calibre will pick up metadata in an opf file stored with any other format in preference to the other two methods. If there's any chance you have some sort of .opf file with the same name as the pdf, it would override the other metadata.