Section 6.4: Understanding PDF Metadata

Aji Annotate uses the iPhone's and iPod Touch's built-in support (the Quartz rendering engine) to display and navigate PDF documents. However, this engine is limited to displaying the document on-screen only and is not able to perform the processing required to access detailed information about the document. This is why Aji Annotate requires the use of the Aji Reader Service, which preprocesses and extracts this "Metadata" from PDF documents, then provides it to Aji Annotate in an efficient, easily-accessible format.

This Metadata includes information about the textual content of the document, including the locations of words on pages -- information which, perhaps surprisingly, is not readily available from PDF documents. This also includes more standard PDF metadata, such as the PDF Outline and Annotations (including PDF links, which are a form of annotation).

The Aji Reader Service takes advantage of the superior processing power of standard computers, along with the more advanced libraries available, to do all of this hard "processing" work and provide the information to Aji Annotate in a way that is more suited to the iPhone's and iPod Touch's capabilities.

So, for any document that you download from your computer using the Aji Reader Service, this process happens automatically and all of the required information is accessible to Aji Annotate. For Web Downloads, however, Aji Annotate is not able to process this information on its own, which is why it has to contact the Aji Reader Service, upload the new PDF document, and then wait for the Aji Reader Service to process the document and return the Metadata information. Of course, this process is handled automatically by Aji Annotate, so there's nothing you have to do except to bring your device onto the same network as your Aji Reader Service.