Adobe ACROBAT READER 7.0 Manual page 15

Description document property settings
The Description panel shows basic information about the document. The title, author,
subject, and keywords may have been set by the person who created the document in the
source application, such as Microsoft Word or Adobe InDesign®, or by the person who
created the PDF document. In Adobe Reader, you cannot add to or edit this document
information.
You can search for these description items in Adobe Reader to find particular documents.
The Keywords section can be particularly useful for narrowing searches. (See About
searching text.) Note that many search engines use the title to describe the document in
their search results list. If a PDF file does not have a title, the file name appears in the
results list instead. A file's title is not necessarily the same as its file name.
The Advanced group box shows which PDF version the document is created in, the page
size, number of pages, and whether the document is tagged. This information is generated
automatically and cannot be modified.