if i develop a custom component and that component internally calling other component such as pdfg ,asssembling, reader extension,encryption etc. how can make use of those services in my custom component programatically.
There are Java API for those services. If you try to import any classes to use the APIs and get errors, don't add the JARs. In component.xml, after <class-path>..</class-path> add this for reader extensions.