A large portion of the Documents class library requires the use of a cache system. This includes almost all of the write support. Documents can contain large number of pages and huge amount of data. Storing all this data in the physical memory is not feasible in most situations. Therefore, the Document library was designed to use an external caching system to store the modified parts of the document.
Using a large cache will also improve the performance when getting page data such as an image or text. The data will be parsed once from the physical file on disk, processed and then stored in the cache. Subsequent calls to the same data will simply retrieve it from the cache without any extra processing.
The LEADTOOLS Document Web Service requires the use of a cache. Web methods are sessionless by nature and with cache support, the service can use SaveToCache and LoadFromCache to save/load the document state in between calls without the need for session state.
In almost all cases, the cache object is initialized and set into Cache at the start of the application and then never touched. The DocumentFactory and Document classes will use this global value for all caching needs.