Types of PDF file
Available/Available (incomplete):
    An incomplete PDF may be missing figures and/or meta-data
Text:
    "Full text (Original)" is direct from the publisher; Full text (rebuilt from scans) is reconstructed full text from computer-read then proof-read scans; "scan (image with OCR)" is the image scan with an underlying, error-prone layer of computer-read but not proof-read full text.
Figures:
    Original or scan image.
Meta-data:
    This is the data you see in a PDF when you select "Document Properties" in Adobe Acrobat Reader. It assists web search engines and databases (or so I'm told).