Section 14: Understanding PDF Processing

iAnnotate uses 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 iAnnotate has to "process" documents in order to get this information into a format that is more readily usable.

This information includes data 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 standard PDF information such as the PDF Outline and existing annotations (including PDF links, which are a form of annotation).

iAnnotate includes built-in support for processing documents on the device. In many cases, this will be sufficent and the use of APS will not be required. However, it is often faster and more convenient to use the Aji PDF Service on your computer for this task, especially for very long or complex/unusual documents. The Aji PDF Service takes advantage of the superior processing power of standard computers to do all of this hard "processing" work and provide the information to iAnnotate in a way that is more suited to the device capabilities.