Adobe ACROBAT READER 7.0 Manual page 16

Advanced document property settings
The Advanced panel shows PDF settings and reading options:
Base URL displays the base Uniform Resource Locator (URL) set for web links in the
document. The base URL is not used if a link contains a complete URL address.
Search Index displays the name of the autoindex associated with the file. (The autoindex
is created in Acrobat.) Opening the file adds the associated index to the list of indexes that
can be searched. (See Searching across multiple Adobe PDF documents.)
The Trapped menu indicates whether trapping is applied to the file. Prepress software uses
this information to determine whether to apply trapping at print time.
Binding affects how the pages are arranged side by side when you view them using the
Continuous - Facing page layout. (See Setting the page layout and orientation.) This is for
matching the reading direction (left to right or right to left) of text in the document. Right
Edge binding is useful for viewing Arabic or Hebrew text or vertical Japanese text.
Language specifies the default language used in the document. (See Using a screen
reader.)