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9.3 Web-Optimized (Linearized) PDFPDFlib can apply a process called linearization to PDF documents (linearized PDF iscalled Optimized in Acrobat 4, and Fast Web View in Acrobat 5 and above). Linearizationreorganizes the objects within a PDF file and adds supplemental information which canbe used for faster access.While non-linearized PDFs must be fully transferred to the client, a Web server cantransfer 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 aPDF document separately. The result is that the first page of the document will be presentedto the user without having to wait for the full document to download from theserver. This provides enhanced user experience.Note that the Web server streams PDF data to the browser, not PDFlib. Instead, PDFlibprepares the PDF files for byteserving. All of the following requirements must be met inorder to take advantage of byteserving PDFs:> The PDF document must be linearized. This can be achieved with the linearize optionin PDF_begin_document( ) as follows:p.begin_document(outfilename, "linearize");In Acrobat you can check whether a file is linearized by looking at its documentproperties (»Fast Web View: yes«).> The Web server must support byteserving. The underlying byterange protocol is partof HTTP 1.1 and therefore implemented in all current Web servers. In particular, thefollowing Web servers support byteserving:Microsoft Internet Information Server (IIS) 3.0 and aboveApache 1.2.1 and above; however, Apache 1.3.14 (but not other versions) has a bugwhich prevents byteserving> The user must use Acrobat as a Browser plugin, and have page-at-a-time downloadenabled in Acrobat (Acrobat 6/7: Edit, Preferences, [General...,] Internet, Allow fast webview; Acrobat 5: Edit, Preferences, General..., Options, Allow Fast Web view). Note that thisis enabled by default.The larger a PDF file (measured in pages or MB), the more it will benefit from linearizationwhen delivered over the Web.Note Linearizing a PDF document generally slightly increases its file size due to the additional linearizationinformation.Temporary storage requirements for linearization. PDFlib must create the full documentbefore it can be linearized; the linearization process will be applied in a separatestep after the document has been created. For this reason PDFlib has additional storagerequirements for linearization. Temporary storage will be required which has roughlythe same size as the generated document (without linearization). Subject to theinmemory option in PDF_begin_document( ) PDFlib will place the linearization data eitherin memory or on a temporary disk file.9.3 Web-Optimized (Linearized) PDF 201