How PDF viewer works on Android

I went through the open source of pdf viewer in android.

My guess is that they convert the pdf pages i开发者_开发知识库n to images. Google by default does not any library functions to parse or display a pdf. Is there any way to render pdf instead of displaying them as image?

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I think it should be easier to use a library. So far I've used http://itextpdf.com/ and it works well... On Java in an App Server :P . Using it with Android should be interesting.