PDFlib 8 Windows COM/.NET Tutorial

3.4 Web-Optimized (Linearized) PDF
PDFlib can apply a process called linearization to PDF documents (linearized PDF is also
called Optimized or Fast Web View). Linearization reorganizes the objects within a PDF
file and adds supplemental information which can be used for faster access.
While non-linearized PDFs must be fully transferred to the client, a Web server can
transfer linearized PDF documents one page at a time using a process called byteserving.
It allows Acrobat (running as a browser plugin) to retrieve individual parts of a
PDF document separately. The result is that the first page of the document will be presented
to the user without having to wait for the full document to download from the
server. This provides enhanced user experience.
Note that the Web server streams PDF data to the browser, not PDFlib. Instead, PDFlib
prepares the PDF files for byteserving. All of the following requirements must be met in
order to take advantage of byteserving PDFs:
> The PDF document must be linearized. This can be achieved with the linearize option
in begin_document( ) as follows:
p.begin_document(outfilename, "linearize");
In Acrobat you can check whether a file is linearized by looking at its document
properties (»Fast Web View: yes«).
> The Web server must support byteserving. The underlying byterange protocol is part
of HTTP 1.1 and therefore implemented in all current Web servers.
> The user must use Acrobat as a Browser plugin, and have page-at-a-time download
enabled in Acrobat (Edit, Preferences, [General...,] Internet, Allow fast web view). Note
that this is enabled by default.
The larger a PDF file (measured in pages or MB), the more it will benefit from linearization
when delivered over the Web.
Note Linearizing a PDF document generally slightly increases its file size due to the additional linearization
information.
Temporary storage requirements for linearization. PDFlib must create the full document
before it can be linearized; the linearization process will be applied in a separate
step after the document has been created. For this reason PDFlib has additional storage
requirements for linearization. Temporary storage will be required which has roughly
the same size as the generated document (without linearization). Subject to the
inmemory option in begin_document( ) PDFlib will place the linearization data either in
memory or on a temporary disk file.
3.4 Web-Optimized (Linearized) PDF 79