Ability to include annotations present in a PDF in the output image

[skela]

Some PDFs have annotations which don't get output to the image when you convert from PDF to UIImage. This is a good thing in most cases I think, but there are scenarios where it would be good to be able to include these annotations. So an ability to optionally include annotations would be awesome.

I'll take a look myself and supply a pull request if I'm able to do it and you agree with the changes ;)