Metadata is supporting information about the PDF document. It can describe properties such as authors, document creation date, reference numbers, information about embedded images, and so on.
There are two areas where metadata can exist in a PDF file:
Document Information Dictionary: To see these fields in Nitro Pro, in the File menu, select Document Properties. This is a set of defined metadata fields (Title, Author, Creator, Producer, CreationDate, ModDate) that store specific types of information.
Metadata stream: A metadata stream is a way to store metadata in a PDF file. As long as the contents of the metadata stream are represented in XMP (Extensible Metadata Platform), anything can be stored in the metadata stream. For example, a photo management application may allow export to a PDF file, and when it does, attach a metadata stream for each image describing the name of the person who took the picture.
NOTE: You cannot view document metadata in Nitro Pro.
Why remove metadata?
The Redaction tools allow you to remove confidential text or images from content that the user can see on the page. Metadata, however, is invisible to many PDF file viewers and editors. Some metadata may be sensitive or privileged information, and therefore unsuitable for public distribution. The Remove Metadata tool in Nitro Pro removes all traces of metadata.
For more information, see Redaction.
The Remove Metadata feature removes all instances of both types of metadata from the PDF document.
To remove metadata:
On the Protect tab, in the Redaction group, click Remove Metadata
A dialog appears, and asks you to confirm that you want to remove all metadata. Click OK.