PDFlib Text Extraction Toolkit (TET) Manual

5 Configuration
5.1 Indexing protected PDF Documents
PDF documents may use the following means of protection:
> A user password may be required for opening the document.
> Permission settings may allow or prevent certain actions, including extracting page
contents.
> A master password may be required for changing permission settings or one of the
passwords.
TET honors PDF permission settings. The password and permission status can be queried
with the pCOS paths encrypt/master, encrypt/user, encrypt/nocopy, etc. as demonstrated
in the dumper sample. pCOS also offers the pcosmode pseudo object which can
be used to determine which operations are allowed for a particular document.
Content extraction status. By default, text and image extraction is possible with TET if
the document can successfully be opened (this is no longer true if the requiredmode option
of TET_open_document( ) was supplied). Depending on the nocopy permission setting,
content extraction may or may not be allowed in restricted pCOS mode (content
extraction is always allowed in full pCOS mode). The following conditional can be used
to check whether content extraction is allowed:
if ((int) tet.pcos_get_number(doc, "pcosmode") == 2 ||
((int) tet.pcos_get_number(doc, "pcosmode") == 1 &&
(int) tet.pcos_get_number(doc, "encrypt/nocopy") == 0))
{
/* content extraction allowed */
}
The need for processing protected documents. PDF permission settings help document
authors to enforce their rights as creators of content, and users of PDF documents
must respect the rights of the document author when extracting text or image contents.
By default, TET will operate in restricted mode and refuse to extract any contents
from such protected documents. However, content extraction does not in all cases automatically
constitute a violation of the author’s rights. Situations where content extraction
may be acceptable include the following:
> Small amounts of content are extracted for quoting (»fair use«).
> Organizations may want to check incoming or outgoing documents for certain keywords
(document screening).
> The document author himself may have lost the master password.
> Search engines index protected documents without making the document contents
available to the user directly (only indirectly by providing a link to the original PDF).
The last example is particularly important: even if users are not allowed to extract the
contents of a protected PDF, they should be able to locate the document in an enterprise
or Web-based search. It may be acceptable to extract the contents if the extracted text is
not directly made available to the user, but only used to feed the search engine’s index
so that the document can be found. Since the user only gets access to the original pro-
5.1 Indexing protected PDF Documents 49