OK. You say you don't want to use external libraries? Well then, have fun writing your own library to parse and render a PDF file. You might want to look at the source for
SumatraPDF[
^] to get an idea of the amount of work you're in for.
Personally, I wouldn't waste 6 months of my life writing a PDF library when there are a ton of them that already exist and do that job for me.