On Mac, the print dialog 'Save to pdf' features captures all types of images and image-like things.
On iPad, the tools I have tried run into problems, e.g.:
On https://en.wikipedia.org/wiki/Random_variable, no MathML is included in the conversion or only that which appears on the first page or two.
On http://www.businessinsider.com/7-gifs-trigonometry-sine-cosine-2013-5, the animated gifs are properly converted to single static images, but surrounding text is lost.
Do any tools work properly on these webpages?